Matlab Find Exact String In Cell Array

will give you the indices into your string to the start of any matching elements. There are times where you have a lot of data in a vector or array and you want to extract a portion of the data for some analysis. I used the following function to find out the indexes for one element of B at a time. The Structure Data Type in Matlab. All variables of all data types in MATLAB are multidimensional arrays. How to find index of a value in cell array. Learn more about cell array, find. This uses the Matlab function ismember ( link ). The search performed by strfind is case sensitive. While the phrase cell array of strings frequently has been used to describe such cell arrays, the phrase is no longer accurate because such a cell array holds character vectors, not strings. The format of the VLOOKUP function is: VLOOKUP(lookup_value,table_array,col_index_num,range_lookup). For any input cell whose text does not contain 'bla', “strfind” returns an empty cell. The num2cell function converts an array that has any data type—even a nonnumeric type. This function uses strcmp or strcmpi to return indices of a list of strings matching an input string. However, before that, let us discuss some special types of arrays. A Structure is a named collection of data representing a single idea or "object". How do I search the cell array for a particular string and get the index that string occupies in the array? So something like:. Code generation does not support using eq to test equality between an enumeration member and a string array, a character array, or a cell array of character arrays. Each index in your cell array should contain one of these strings. Use “isempty” and “cellfun” with the “find” function to find the empty cells. Array Names and Matrix Functions in Microsoft Excel ® This is a demonstration of a convenient feature of the Excel spreadsheet that is not well documented in the online help files. Using Arrays with Functions and Operators. The cell array is surrounded by curly brackets { }. A format of a cell is: the linear index is in the superscript while the 2d coordinates are in subscript. say hhh is the first element of B. " Therefore, after your fourth assignment to legends, you actually have a cell array containing two elements, a cell array and a string. Matlab: find a string within a cell array of strings Arnabocean. All other cells or fields of A are unaltered in B. I would like to match a string in a list of other strings (cell array). If strmatch does not find str in strarray, x is an empty matrix ([]). Using Array Formulas in Excel OFC-10 What Are Array Formulas? Imagine being able to tell via a formula if your data is correct, such as determining that the successive cells increase by 1, or whether 2 ranges have duplicate values. This is when heterogeneous containers, like the CELL, comes handy. find all elements in the array a that has value 1 or 2). The exact form of grad depends on the input network or learnable parameters. Matlab: using strfind to get exact match. How do I search the cell array for a particular string and get the index that string occupies in the array? So something like:. Do you want to scan the cell array and convert the cells that have numbers in them to strings? Or do you want 5 separate string variables, like x1, x2, x3, x4, and x5?. Find one of strings into cell array. Matched text, returned as a string scalar if validStrings is a string array or as a character vector if validStrings is a cell array of character vectors. TechnicalQuestion Issues with creating a way to search through a string array / cell array (self. it is 1*12000. I need to find every position in the array names that has the string 'Freq' and then pull all data rows in that column, so this is the code i'm using:. second dimension is 1 or more, and all remaining dimensions are 1. You need to put them into the cell array at the time you generate them (or at least before X changes). If strmatch does not find str in strarray, x is an empty matrix ([]). MATLAB Central contributions by Stephen Cobeldick. If no data type is. After placing the MEX file in your MATLAB path (compile the C source if necessary), run headerdump (1) for a simple example. MATLAB Forum - String in Cell array suchen - Hallo, ich habe einen Cell Array der wie folgt aussehen kann a=('Hallo' 'Hallo' Hallo'. There is a cost with doing this, which is that your program will slow down, if you do it often enough. C = []; and you can add a string to the end of a cell array by e. Your response for the cell string method worked. All other cells or fields of A are unaltered in B. Cell Arrays Strings Inputs/outputs Structs Built-in functions Purely numeric functions Most MATLAB functions, like sin, cos, log, and many others, work regardless of the size of the input. When you do. I want to find a certain row depending on the characters. See screenshot: 2. Find one of strings into cell array. Notice the two 160 characters at the end of the string ([67 69 82 84] are the character codes for CERT). MATLAB offers several ways to display the value of. deblank Strip trailing blanks from the end of a string findstr Find one string within another lower Convert string to lower case strcat String concatenation strcmp Compare strings strcmpi Compare strings, ignoring case strjust Justify a character array strmatch Find possible matches for a string strncmp Compare the first n characters of strings. Below are several examples of printing information from variables using fprintf. Try copies of variables, especially when cell arrays or structs are involved. Legend properties control the appearance and behavior of a Legend object. Strings, Cells, Structs, Containers, and Sets In this section, we examine strings and string operations as well as two very important Matlab data structures: cell arrays, and structs. The eval_string evaluate a string containing MATLAB expressions (typically used with the helper macros @mget and @mput The mxcall function calls a given MATLAB function and returns the result In general, the mat"" custom string literal is the preferred method to interact with the MATLAB engine. I have a cell array in Matlab 7. celldisp Displays cell array. Notice the use of %s to print a string, and %d to print an integer, and %f to print a number with a decimal (a floating point number). Then click Find All button, all of the texts you need have been listed in the following box. My problem is that when using regexp a number of cells containing similar text are being identified and corresponding columns are removed from the dataset. There is a cell in name of 'CELL'. MATLAB allows you to use your data in another application that reads ASCII files. Matlab also has data types called "cells" and "structures", which are best found out about by reading the Matlab documentation. (cell) A cell array with missing sensor data filled in 2. Below are two examples of the EXACT function used with hardcoded strings. Dim myArray(number of elements) As Type. Problems finding exact match for a string. Pre-allocating Space. Use "isempty" and "cellfun" with the "find" function to find the empty cells. This method uses the Matlab function strfind ( link ). Fields to search in the WMSLayer objects, specified as a string, string array, character vector, or cell array of character vectors. will give you the indices into your string to the start of any matching elements. The structure of the cell array is like this: A is a 27x1 cell where each of the 27 rows has 500000 cell entries (numeric values between -1 and 999). Note, you can create an empty cell array by setting it to an empty cell, e. The cell array is surrounded by curly brackets { }. You have to use the char function to convert from a cell array of strings to a character array (a string like I am use to). A is an m x n character array (I think that is the right term. This function uses strcmp or strcmpi to return indices of a list of strings matching an input string. Start studying Matlab Midterm. The remainder consists of all characters from the first delimiter on. I think he wanted the 3 to be a number, if you look at his desired output. x = strmatch(str, strarray) looks through the rows of the character array or cell array of character vectors strarray to find character vectors that begin with the text contained in str, and returns the matching row indices. fprintf ME 352, Fall 2008 page 1/6 Using fprintf in Matlab The fprintf statement provides control the way that numeric and string data are printed to the command window or a le. function idx = findpattern(in_array, pattern) %FINDPATTERN Find a pattern in an array. "Braces are used to form cell arrays. To do this task, use the EXACT function. Find a value with cell array. Each of 'RE', 'RW', appears to have 4 different values for each day (day1, day2,. But guessing this detail wastes time. Your response for the cell string method worked. Most expressions take such arrays and return such arrays. 1 In other words, although both " phrase " and " list " are arrays of characters, only " phrase " is big enough to contain the string value " "Enter age: " ". regexp does not support international character sets. They are similar to brackets [ ] except that nesting levels are preserved. Each row from each character array in the cell array becomes a row in C, automatically padded with blank spaces as needed. It turns out that there are more efficient and more stable methods to do this (L/U decomposition with pivoting, for example). They basically allow you to "build up" bigger and more interesting collections of data by naming sub-parts of information. Code generation does not support using eq to test equality between an enumeration member and a string array, a character array, or a cell array of character arrays. Call the content of cell 2,2 of the cell array cell. Transpose on a one-dimensional array does nothing. will give you the indices into your string to the start of any matching elements. The num2cell function converts an array that has any data type—even a nonnumeric type. 2 containing a bunch of strings. " Therefore, after your fourth assignment to legends, you actually have a cell array containing two elements, a cell array and a string. For example, compare the output of numel for a character vector and string:. Sharpen your programming skills while having fun!. Using strings in Matlab. But your method is more flexible than mine. Functions that allow one to find, replace, and separate strings are introduced. Find in a cell array? Asked by Just a casual MATLAB coder dropping by this older thread on a hunt for answers. For example, look up cell A1 - "R8923" in a table D1:F560 that has "R8923-01 rev. Obviously, you can use filter(), [] or slice() to select which column to. Either one can also be a character array with the right number of rows. Find a value with cell array. Loop Through a Cell Array. We also discuss the new (2008b) container. es BE0B17MTB{ Matlab Lecture 6: Data Types: Cell, String, and Structure 6 / 56. A is an m x n character array (I think that is the right term. Try copies of variables, especially when cell arrays or structs are involved. Most string functions support both types. Just about every possible type of variable is supported, though some in more detail than others. Now, in your second case, if you still were to use strcmp for the comparison, you would indeed need cellfun (or an explicit loop) to break your Channels cell array into individual strings as you can't strcmp two cell arrays together (expect if they're the same size but then it's a different behaviour). For example, maybe you want to plot column 1 vs column 2, or you want the integral of data between x = 4 and x = 6, but your vector covers 0 < x < 10. Dim myArray(number of elements) As Type. Find the closest or nearest value with array formula. Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. For example, the code below indicates a 1 x 3 "cell" variable containing a 2x2 integer matrix, a 1x5 character string and a 1x10 row vector of real numbers. For example, you may want to attach a time or date stamp to the end of a variable name. A cell array is a rectangular set of data similar to a matrix but it can hold any type of data such as text, numbers, and/or vector. So, your original array was a cell array of cells with a single string. If A is a cell array of character vectors or a string array, then sort(A) sorts the elements according to the code order for the UTF-16 character encoding scheme. Gradients of the loss, specified as a dlarray, a numeric array, a cell array, a structure, or a table. Vidar's solution does work in that case (quite nicely), so is more general. String using a Matlab cell array which has been converted to a char array but it doesn't work. They are similar to brackets [ ] except that nesting levels are preserved. MATLAB Answers. GPU Arrays Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™. Use the Go To command to quickly find and select all cells that contain specific types of data, such as formulas. Structure Functions fieldnamesReturns field names in a structure array. This lead me to think that I wanted to use a cell of some form like I did above. Community Home;. This method uses the Matlab function strfind ( link ). I Most of the functions work with both string types. =COUNTA(A2:A7349)-COUNT(A2:A7349) For more information see Tip 52:Cell Counting Techniques (j-walk), additional links on counting. I = STRMATCH(STR, STRARRAY) looks through the rows of the character array or cell array of strings STRARRAY to find strings that begin with the string contained in STR, and returns the matching row indices. Thus, it is convenient to have a sensible naming convention while you create your models inside the tomograms, as it will facilitate accessing them if. Since a couple of days, I constantly receive the same error while using MATLAB which happens at some point with dlopen. Call the content of cell 2,2 of the cell array cell. My problem is that in using regexpi or regexp, it misidentifies the location of the string if it finds it as a substring. Strfind looks for a specific string within a cell array of strings, but it tries to find it in any part of each string. However, if A is a string scalar, numel returns 1 because it is a single element of a string array. Each index in your cell array should contain one of these strings. To do this task, use the EXACT function. (cell) A cell array with missing sensor data filled in 2. The size of this matrix or array is a minimum of 0-by-0 and this can grow up to a matrix or array of any size. Find the closest or nearest value with array formula. Try copies of variables, especially when cell arrays or structs are involved. function idx = findpattern(in_array, pattern) %FINDPATTERN Find a pattern in an array. com I just wanted to jot down a few points about Matlab programming. For a cell array case_expression, at least one of the elements of the cell array matches switch_expression, as defined above for numbers, strings and objects. A is an m x n character array (I think that is the right term. Toggle Main Navigation. as a "character array", the term used in the rest of Matlab. When manipulations or computations need to be performed on all or a subset of values in a cell array, one useful function that can be utilized is cellfun. In Matlab, arrays are dynamic in size, meaning, whenever you need a larger array, you can just index based on this larger number and Matlab will automajically resize your original array to be the new bigger size. Matlab: using strfind to get exact match. I have a cell array as attached, I want to find the row number which contains a specified string, such as 'bore', I know how to write a for-loop to compare the element one by one, but, is there any easier way to do this?. I need to find every position in the array names that has the string 'Freq' and then pull all data rows in that column, so this is the code i'm using:. If strmatch does not find str in strarray, x is an empty matrix ([]). I can refer to the cell itself with standard parentheses - so c(3,3) is a cell - or the contents with the curly braces - so c{3,3} is a character array above. com wrote: > I have a cell array consisting of numbers, strings, and empty arrays. This method uses the Matlab function strfind ( link ). Matlab also has data types called "cells" and "structures", which are best found out about by reading the Matlab documentation. For a cell array case_expression, at least one of the elements of the cell array matches switch_expression, as defined above for numbers, strings and objects. In the case of a list of strings this is very useful as the size issue is properly taken care of. How do I search the cell array for a particular string and get the index that string occupies in the array? So something like:. This uses the Matlab function ismember ( link ). The search performed by strfind is case sensitive. The exact form of grad depends on the input network or learnable parameters. Find a vector of string in a Cell array. This uses the Matlab function ismember ( link ). The "string" class type is a new addition to C++, which did not exist in traditional C. However, "strfind" returns a cell array of indices. The for loop allows us to repeat certain commands. The EXACT function compares two text strings in a case-sensitive manner. If Ujourney{1,1} is expected to be a character array then you cannot put a string into a particular column of a character array: strings are row vectors, not column vectors. What data type is Ujourney{1,1} expected to be? The only data type that you can store strings in is cell arrays. Each of 'RE', 'RW', appears to have 4 different values for each day (day1, day2,. Description. a string, a string array and character array the exact version), individual char are stored as unsigned values from Matlab also refers to "cell strings"; see. Toggle Main Navigation. Here's my code: To test, I filled an array with 100,000 random strings, picked one of the strings to find, then timed JP. This method uses the Matlab function strfind ( link ). MATLAB Central. If one input is a categorical array, the other input can be a categorical array, a cell array of character vectors, or a single character vector. Each row from each character array in the cell array becomes a row in C, automatically padded with blank spaces as needed. But your method is more flexible than mine. How is this useful? MATLAB has a few powerful functions for operating on logical arrays: find : Find indices of nonzero. Vlookup to match partial text string in array and return value I'm am trying to perform a vlookup in an array to find text with other text info. Strfind looks for a specific string within a cell array of strings, but it tries to find it in any part of each string. The traditional method for handling character strings is to use an array of characters. Find in a cell array? Asked by Just a casual MATLAB coder dropping by this older thread on a hunt for answers. (char) Name of a text file, including the extension. If a string is specified as first argument, the buffer is made one item larger than the length of the string so that the last element in the array is a NUL termination character. The following table shows the required format for grad for possible inputs to sgdmupdate. I also give recommendations on when best to use string, char, or cell for text and share some of our thinking on the future. The output from logic operations are \logical"-type arrays of ones and zeros. find a string from a cell array. Specifically, this is about finding a string within another cell array of strings, where the thing I’m really interested in is the index of the cell array where the reference string occurs. I have a cell array in Matlab 7. 2 Sorting and Searching. Here is a way using regular expressions, which I think is far less efficient than @Divakar's strcmp solution, but that could be informative anyway. The output from logic operations are \logical"-type arrays of ones and zeros. Most expressions take such arrays and return such arrays. Notice the use of %s to print a string, and %d to print an integer, and %f to print a number with a decimal (a floating point number). Cell arrays are accessed like normal arrays, but using curly braces instead of standard parentheses, so if I have a cell array c, I might say c{3,2} = 16, followed by c{3,3} = 'cat'. x = strmatch('str', STRS) looks through. How do I search the cell array for a particular string and get the index that string occupies in the array? So something like:. Hopefully this is a fairly simple question, but I am new to Matlab and am having difficulty converting a cell array of cells to a cell array of strings. Using Array Formulas in Excel OFC-10 What Are Array Formulas? Imagine being able to tell via a formula if your data is correct, such as determining that the successive cells increase by 1, or whether 2 ranges have duplicate values. Input the text that you need in the Find what dropdown list. A is an m x n character array (I think that is the right term. x = strmatch(str, strarray) looks through the rows of the character array or cell array of character vectors strarray to find character vectors that begin with the text contained in str, and returns the matching row indices. Learn more about cell arrays MATLAB Answers. There is a cell in name of 'CELL'. "Braces are used to form cell arrays. So, your original array was a cell array of cells with a single string. The for loop allows us to repeat certain commands. Description. I didn't compare regexp in MATLAB with other languages. Find the exact match of a string from a cell Learn more about matlab, string, cell arrays. com wrote: > I have a cell array consisting of numbers, strings, and empty arrays. MATLAB Forum - String aus Cell Array erhalten - Hallo! Ich mache mich gerade mit den Cell Arrays von Matlab bekannt und muss sagen, Sachen reinschreiben kann ich jetzt gut - Sachen auslesen ist irgendwie komplizierter. function idx = findpattern(in_array, pattern) %FINDPATTERN Find a pattern in an array. Creating strings in a regular MATLAB array requires that all strings in the array be of the same length. MATLAB - Arrays. Instead of referring to the first revenue variable as Rev1, you can refer to it by using the array name and an index into the array, such as REVENUE[I] (assuming that I has a value of 1). The exact form of grad depends on the input network or learnable parameters. Now, in your second case, if you still were to use strcmp for the comparison, you would indeed need cellfun (or an explicit loop) to break your Channels cell array into individual strings as you can't strcmp two cell arrays together (expect if they're the same size but then it's a different behaviour). If 'Search criteria = and <> must apply to whole cells' is enabled on the Tools - Options - OpenOffice. The function searches the values of the specified fields in the WMSLayer objects for a partial or exact match with querystr. So the difference is the number of TEXT cells. What I want are the indices where the value -1 occurs, since I have to replace them afterwards. Find the longest text string in a range of cells. String functions A complete reference of all of MATLAB's string functions can be obtained by typing 'help strfun' at the MATLAB prompt. 1’ I do not want it to match with this expression because this is string stands. strcmpi(S,T) when either S or T is a cell array of strings, returns an array the same size as S and T containing 1 for those elements of S and T that match except for case, and 0 otherwise. Matlab: using strfind to get exact match. A collection of strings can be created in either of the following two ways: As the rows of a character array via strvcat; As a cell array of strings via the curly braces You can convert between character array and cell array of strings using char and cellstr. Rectangular, delimited ASCII data file from an array. txt' Outputs: 1. With some practice in parsing strings in Matlab, you can extract a new cell array from a previous cell array, greping only the cell array elements that include some given string in their name. MATLAB Forum - String aus Cell Array erhalten - Hallo! Ich mache mich gerade mit den Cell Arrays von Matlab bekannt und muss sagen, Sachen reinschreiben kann ich jetzt gut - Sachen auslesen ist irgendwie komplizierter. [token, rem] = strtok() returns the remainder rem of the original string. The field names of S are timer object property names and the field values are the corresponding property values. It's somewhat confusing so let's make an analogy. ischar(S) tells if S is a string variable. If Alex is getting Out Of Memory for an array that small, then chances are quite high that Alex is using a 32 bit version of Matlab, in which case Matlab *does* restrict arrays. Toggle Main Navigation. However, before that, let us discuss some special types of arrays. num2cell Converts numeric array to cell array. How is this useful? MATLAB has a few powerful functions for operating on logical arrays: find : Find indices of nonzero. Compare one cell to another cell. strcmpi(S,T) when either S or T is a cell array of strings, returns an array the same size as S and T containing 1 for those elements of S and T that match except for case, and 0 otherwise. Matlab also has data types called "cells" and "structures", which are best found out about by reading the Matlab documentation. C{end+1} = ‘hello’; * Write code to count how many times the (exact) string ‘hello’ occurs in your array. The structure of the cell array is like this: A is a 27x1 cell where each of the 27 rows has 500000 cell entries (numeric values between -1 and 999). JP has a good post about finding exact matches in arrays. There are 140 names in the array. My code for cells uses braces. Subject: [matlab] Comparing elements of arrays of different Sizes Hello all, Can anybody help me to find out the method to compare the elements of different sized arrays ? I have one array of 100 elements and I am generating second array within a loop having some arbitrary number of elements. matlab Newsgroup [email protected] MATLAB does not have a built-in function that will compare two strings and determine whether the first string is "less than", "equal to", or "greater than" a second string. Each element of a string array stores a sequence of characters. The field names of S are timer object property names and the field values are the corresponding property values. I need to find every position in the array names that has the string 'Freq' and then pull all data rows in that column, so this is the code i'm using:. Description. Use "isempty" and "cellfun" with the "find" function to find the empty cells. Inside a structure are a list of fields each being a variable name for some sub-piece of data. Data Types Available in MATLAB. The values 3200, 2700, and 2000 are returned to the three-cell columnar array. I Join the array with delimiters around all the values, then use Instr to see if it's there. This function uses strcmp or strcmpi to return indices of a list of strings matching an input string. You need to put them into the cell array at the time you generate them (or at least before X changes). Any leading delimiters are ignored. You may also have variable names stored in a string or cell array that you want to instantiate as variables. For a cell array case_expression, at least one of the elements of the cell array matches switch_expression, as defined above for numbers, strings and objects. MATLAB Central. ASCII Chart in Matlab In this article we have three goals: first, we're going to develop an ASCII chart to understand instructions char and double in Matlab; second, we're going to work with a simple ASCII conversion technique as an example of simple encoding, and third, we're going to develop a rot13 method, which happens to be another encoding technique. But 300K keywords in a single expression will be too much I believe (don't know exact limit). If you want to repeat some action in a predetermined way, you can use the for loop. The for loop allows us to repeat certain commands. (cell) A cell array with missing sensor data filled in 2. Matlab: find a string within a cell array of strings Method 1. fprintf ME 352, Fall 2008 page 1/6 Using fprintf in Matlab The fprintf statement provides control the way that numeric and string data are printed to the command window or a le. Find in a cell array? Asked by Just a casual MATLAB coder dropping by this older thread on a hunt for answers. Each row from each character array in the cell array becomes a row in C, automatically padded with blank spaces as needed. The output from logic operations are \logical"-type arrays of ones and zeros. The string is already a character array, in Matlab is way more convenient to work with cells if you have to work with characters. So I want to find the positions (values) and calculate the mean for each day. In this section, we will consider in detail two classical algorithms for sorting and searching—binary search and mergesort—along with several applications where their efficiency plays a critical role. Cell arrays in MATLAB are multidimensional arrays whose elements are copies of other arrays. The selected cells are visualized. There are several ways to check if a cell contains text and the case of the text matters to you. A Structure is a named collection of data representing a single idea or "object". The traditional method for handling character strings is to use an array of characters. Cell arrays are accessed like normal arrays, but using curly braces instead of standard parentheses, so if I have a cell array c, I might say c{3,2} = 16, followed by c{3,3} = 'cat'. They are similar to brackets [ ] except that nesting levels are preserved. The cell function. Printing a string array above a table of numerical values, for example, can help you quickly make sense of the column and row information. Note, you can create an empty cell array by setting it to an empty cell, e. In this chapter, we will discuss multidimensional arrays. Headings = [time, speed, distance] Now, I want to have a variable that uses the text inside "Headings" as its name with 1,2,3,4. The num2cell function converts an array that has any data type—even a nonnumeric type. Learn more about cell arrays. " Therefore, after your fourth assignment to legends, you actually have a cell array containing two elements, a cell array and a string. it is 1*12000. Please click below onto the label to load the interactive demonstration on MATLAB matrix indexing. Cell arrays are accessed like normal arrays, but using curly braces instead of standard parentheses, so if I have a cell array c, I might say c{3,2} = 16, followed by c{3,3} = 'cat'. The otherwise block is optional and executes only when no case is true. However, “strfind” returns a cell array of indices. A typical use is to store short pieces. The eval_string evaluate a string containing MATLAB expressions (typically used with the helper macros @mget and @mput The mxcall function calls a given MATLAB function and returns the result In general, the mat"" custom string literal is the preferred method to interact with the MATLAB engine. matlab Newsgroup [email protected] GPU Arrays Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™. I also give recommendations on when best to use string, char, or cell for text and share some of our thinking on the future. function idx = findpattern(in_array, pattern) %FINDPATTERN Find a pattern in an array. For example, you may want to attach a time or date stamp to the end of a variable name. Array Names and Matrix Functions in Microsoft Excel ® This is a demonstration of a convenient feature of the Excel spreadsheet that is not well documented in the online help files. You need to put them into the cell array at the time you generate them (or at least before X changes). Here, fimanipu-. Hopefully this is a fairly simple question, but I am new to Matlab and am having difficulty converting a cell array of cells to a cell array of strings. so if the string doesn't exist do something. Inside a structure are a list of fields each being a variable name for some sub-piece of data. Operations on the 2-D instances of these arrays are designed to act more or less like matrix operations in linear algebra.