How to Read in Text Files Matlab

MATLAB - Data Import

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Importing data in MATLAB means loading data from an external file. The importdata function allows loading various data files of unlike formats. It has the post-obit v forms −

Sr.No.	Function & Description
1	A = importdata(filename) Loads information into array A from the file denoted past filename.
2	A = importdata('-pastespecial') Loads data from the organisation clipboard rather than from a file.
3	A = importdata(___, delimiterIn) Interprets delimiterIn every bit the column separator in ASCII file, filename, or the clipboard data. You can use delimiterIn with any of the input arguments in the above syntaxes.
iv	A = importdata(___, delimiterIn, headerlinesIn) Loads information from ASCII file, filename, or the clipboard, reading numeric data starting from line headerlinesIn+1.
5	[A, delimiterOut, headerlinesOut] = importdata(___) Returns the detected delimiter graphic symbol for the input ASCII file in delimiterOut and the detected number of header lines in headerlinesOut, using any of the input arguments in the previous syntaxes.

By default, Octave does non have support for importdata() function, so you lot will have to search and install this parcel to make following examples piece of work with your Octave installation.

Example ane

Let us load and display an epitome file. Create a script file and blazon the following lawmaking in it −

filename = 'smile.jpg'; A = importdata(filename); paradigm(A);        

When y'all run the file, MATLAB displays the image file. Nonetheless, you must store it in the current directory.

Case two

In this example, we import a text file and specify Delimiter and Column Header. Let us create a space-delimited ASCII file with column headers, named weeklydata.txt.

Our text file weeklydata.txt looks similar this −

SunDay  MonDay  TuesDay  Midweek  Thursday  Friday  SaturDay 95.01   76.21   61.54    40.57       55.79    lxx.28   81.53 73.11   45.65   79.nineteen    93.55       75.29    69.87   74.68 sixty.68   41.85   92.18    91.69       81.32    xc.38   74.51 48.threescore   82.xiv   73.82    41.03       0.99     67.22   93.xviii 89.xiii   44.47   57.63    89.36       13.89    xix.88   46.60        

Create a script file and type the post-obit code in it −

filename = 'weeklydata.txt'; delimiterIn = ' '; headerlinesIn = 1; A = importdata(filename,delimiterIn,headerlinesIn);  % View information for g = [1:vii]    disp(A.colheaders{1, k})    disp(A.data(:, k))    disp(' ') stop        

When you lot run the file, it displays the following event −

Sun    95.0100    73.1100    60.6800    48.6000    89.1300   Mon    76.2100    45.6500    41.8500    82.1400    44.4700   TuesDay    61.5400    79.1900    92.1800    73.8200    57.6300  WednesDay    40.5700    93.5500    91.6900    41.0300    89.3600   ThursDay    55.7900    75.2900    81.3200    0.9900    xiii.8900   Fri    70.2800    69.8700    90.3800    67.2200    19.8800  Sat    81.5300    74.6800    74.5100    93.1800    46.6000        

Example 3

In this instance, allow us import data from clipboard.

Copy the post-obit lines to the clipboard −

Mathematics is uncomplicated

Create a script file and type the following lawmaking −

A = importdata('-pastespecial')        

When y'all run the file, it displays the following consequence −

A =     'Mathematics is simple'        

Depression-Level File I/O

The importdata office is a high-level function. The depression-level file I/O functions in MATLAB allow the almost control over reading or writing information to a file. Notwithstanding, these functions demand more detailed information about your file to work efficiently.

MATLAB provides the following functions for read and write operations at the byte or character level −

Office	Description
fclose	Close one or all open files
feof	Test for end-of-file
ferror	Information about file I/O errors
fgetl	Read line from file, removing newline characters
fgets	Read line from file, keeping newline characters
fopen	Open file, or obtain information about open files
fprintf	Write data to text file
fread	Read data from binary file
frewind	Motility file position indicator to beginning of open up file
fscanf	Read data from text file
fseek	Motility to specified position in file
ftell	Position in open file
fwrite	Write data to binary file

Import Text Information Files with Depression-Level I/O

MATLAB provides the following functions for depression-level import of text data files −

• The fscanf function reads formatted data in a text or ASCII file.

• The fgetl and fgets functions read i line of a file at a time, where a newline character separates each line.

• The fread function reads a stream of data at the byte or bit level.

Example

We have a text information file 'myfile.txt' saved in our working directory. The file stores rainfall data for 3 months; June, July and Baronial for the twelvemonth 2012.

The data in myfile.txt contains repeated sets of time, month and rainfall measurements at five places. The header data stores the number of months M; then we have One thousand sets of measurements.

The file looks similar this −

Rainfall Information Months: June, July, August   M = 3 12:00:00 June-2012 17.21  28.52  39.78  16.55 23.67 xix.fifteen  0.35   17.57  NaN   12.01 17.92  28.49  17.forty  17.06 11.09 9.59   9.33   NaN    0.31  0.23  10.46  13.17  NaN    14.89 19.33 xx.97  nineteen.fifty  17.65  14.45 xiv.00 18.23  ten.34  17.95  sixteen.46 nineteen.34 09:10:02 July-2012 12.76  sixteen.94  14.38  11.86 sixteen.89 20.46  23.17  NaN    24.89 xix.33 30.97  49.50  47.65  24.45 34.00 xviii.23  thirty.34  27.95  16.46 nineteen.34 30.46  33.17  NaN    34.89  29.33 xxx.97  49.50  47.65  24.45 34.00 28.67  xxx.34  27.95  36.46 29.34 xv:03:40 Baronial-2012 17.09  16.55  19.59  17.25 19.22 17.54  eleven.45  13.48  22.55 24.01 NaN    21.19  25.85  25.05 27.21 26.79  24.98  12.23  sixteen.99 18.67 17.54  eleven.45  xiii.48  22.55 24.01 NaN    21.nineteen  25.85  25.05 27.21 26.79  24.98  12.23  16.99 18.67        

We will import information from this file and display this information. Take the following steps −

• Open up the file with fopen part and get the file identifier.

• Describe the data in the file with format specifiers, such as '%s' for a string, '%d' for an integer, or '%f' for a floating-point number.

• To skip literal characters in the file, include them in the format description. To skip a data field, use an asterisk ('*') in the specifier.

  For example, to read the headers and return the single value for M, we write −

  M = fscanf(fid, '%*southward %*south\northward%*southward %*south %*due south %*due south\nM=%d\n\n', ane);            

• By default, fscanf reads data according to our format description until it does non observe any lucifer for the data, or it reaches the stop of the file. Hither we will use for loop for reading 3 sets of data and each time, information technology will read seven rows and 5 columns.

• We will create a structure named mydata in the workspace to store data read from the file. This construction has three fields - fourth dimension, month, and raindata array.

Create a script file and type the following code in it −

filename = '/data/myfile.txt'; rows = 7; cols = 5;   % open up the file fid = fopen(filename);   % read the file headers, find M (number of months) M = fscanf(fid, '%*s %*s\n%*s %*s %*southward %*south\nM=%d\n\northward', one);   % read each set of measurements for n = 1:Chiliad    mydata(n).time = fscanf(fid, '%s', 1);    mydata(due north).month = fscanf(fid, '%southward', 1);      % fscanf fills the array in cavalcade order,    % then transpose the results    mydata(n).raindata  = ...       fscanf(fid, '%f', [rows, cols]); stop for north = 1:M    disp(mydata(north).fourth dimension), disp(mydata(n).month)    disp(mydata(n).raindata) end   % close the file fclose(fid);        

When you run the file, it displays the following result −

12:00:00 June-2012    17.2100   17.5700   11.0900   13.1700   fourteen.4500    28.5200       NaN    nine.5900       NaN   14.0000    39.7800   12.0100    9.3300   14.8900   18.2300    16.5500   17.9200       NaN   19.3300   ten.3400    23.6700   28.4900    0.3100   20.9700   17.9500    19.1500   17.4000    0.2300   19.5000   16.4600    0.3500   17.0600   ten.4600   17.6500   19.3400  09:10:02 July-2012    12.7600       NaN   34.0000   33.1700   24.4500    16.9400   24.8900   18.2300       NaN   34.0000    fourteen.3800   19.3300   30.3400   34.8900   28.6700    11.8600   30.9700   27.9500   29.3300   thirty.3400    16.8900   49.5000   16.4600   thirty.9700   27.9500    20.4600   47.6500   nineteen.3400   49.5000   36.4600    23.1700   24.4500   xxx.4600   47.6500   29.3400  xv:03:40 August-2012    17.0900   13.4800   27.2100   eleven.4500   25.0500    16.5500   22.5500   26.7900   13.4800   27.2100    19.5900   24.0100   24.9800   22.5500   26.7900    17.2500       NaN   12.2300   24.0100   24.9800    nineteen.2200   21.1900   16.9900       NaN   12.2300    17.5400   25.8500   18.6700   21.1900   16.9900    11.4500   25.0500   17.5400   25.8500   18.6700        

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Source: https://www.tutorialspoint.com/matlab/matlab_data_import.htm

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