Matlab Read Text File Line by Line With Delimiter

MATLAB - Information Import

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 following five forms −

Sr.No.	Function & Description
ane	A = importdata(filename) Loads data into array A from the file denoted by filename.
2	A = importdata('-pastespecial') Loads information from the system clipboard rather than from a file.
3	A = importdata(___, delimiterIn) Interprets delimiterIn equally the column separator in ASCII file, filename, or the clipboard data. You can use delimiterIn with any of the input arguments in the higher up syntaxes.
4	A = importdata(___, delimiterIn, headerlinesIn) Loads data from ASCII file, filename, or the clipboard, reading numeric information starting from line headerlinesIn+one.
5	[A, delimiterOut, headerlinesOut] = importdata(___) Returns the detected delimiter grapheme for the input ASCII file in delimiterOut and the detected number of header lines in headerlinesOut, using whatever of the input arguments in the previous syntaxes.

By default, Octave does not have support for importdata() function, so y'all volition have to search and install this package to make following examples piece of work with your Octave installation.

Example 1

Let us load and brandish an epitome file. Create a script file and type the following code in information technology −

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

When you lot run the file, MATLAB displays the epitome file. However, you must store it in the electric current directory.

Importing Imange Files

Example 2

In this example, nosotros import a text file and specify Delimiter and Cavalcade Header. Allow the states create a space-delimited ASCII file with column headers, named weeklydata.txt.

Our text file weeklydata.txt looks like this −

SunDay  Mon  TuesDay  WednesDay  ThursDay  FriDay  Sat 95.01   76.21   61.54    40.57       55.79    lxx.28   81.53 73.xi   45.65   79.19    93.55       75.29    69.87   74.68 60.68   41.85   92.eighteen    91.69       81.32    90.38   74.51 48.threescore   82.14   73.82    41.03       0.99     67.22   93.18 89.13   44.47   57.63    89.36       thirteen.89    xix.88   46.lx

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

filename = 'weeklydata.txt'; delimiterIn = ' '; headerlinesIn = one; A = importdata(filename,delimiterIn,headerlinesIn);  % View data for k = [1:7]    disp(A.colheaders{ane, k})    disp(A.data(:, k))    disp(' ') end

When y'all run the file, information technology displays the following effect −

Sun    95.0100    73.1100    threescore.6800    48.6000    89.1300   MonDay    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    seventy.2800    69.8700    90.3800    67.2200    19.8800  SaturDay    81.5300    74.6800    74.5100    93.1800    46.6000

Case 3

In this example, permit us import information from clipboard.

Copy the following lines to the clipboard −

Mathematics is elementary

Create a script file and blazon the following code −

A = importdata('-pastespecial')

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

A =     'Mathematics is simple'

Low-Level File I/O

The importdata function is a high-level part. The depression-level file I/O functions in MATLAB allow the most control over reading or writing information to a file. Yet, these functions need 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 −

Function	Description
fclose	Shut 1 or all open up 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 up file, or obtain data about open files
fprintf	Write information to text file
fread	Read information from binary file
frewind	Motility file position indicator to beginning of open file
fscanf	Read data from text file
fseek	Move to specified position in file
ftell	Position in open file
fwrite	Write data to binary file

Import Text Data Files with Low-Level I/O

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

The fscanf function reads formatted information in a text or ASCII file.
The fgetl and fgets functions read one line of a file at a fourth dimension, where a newline character separates each line.
The fread function reads a stream of information at the byte or bit level.

Example

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

The data in myfile.txt contains repeated sets of time, month and rainfall measurements at v places. The header data stores the number of months M; so we have Grand sets of measurements.

The file looks like this −

Rainfall Data Months: June, July, August   M = 3 12:00:00 June-2012 17.21  28.52  39.78  sixteen.55 23.67 19.xv  0.35   17.57  NaN   12.01 17.92  28.49  17.forty  17.06 11.09 9.59   ix.33   NaN    0.31  0.23  x.46  thirteen.17  NaN    14.89 19.33 20.97  19.l  17.65  fourteen.45 fourteen.00 18.23  10.34  17.95  16.46 nineteen.34 09:10:02 July-2012 12.76  16.94  fourteen.38  eleven.86 16.89 20.46  23.17  NaN    24.89 nineteen.33 xxx.97  49.50  47.65  24.45 34.00 18.23  xxx.34  27.95  16.46 19.34 xxx.46  33.17  NaN    34.89  29.33 thirty.97  49.50  47.65  24.45 34.00 28.67  30.34  27.95  36.46 29.34 xv:03:forty August-2012 17.09  16.55  19.59  17.25 nineteen.22 17.54  11.45  13.48  22.55 24.01 NaN    21.19  25.85  25.05 27.21 26.79  24.98  12.23  16.99 18.67 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  16.99 18.67

Nosotros will import data from this file and display this data. Take the following steps −

Open the file with fopen office 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 −
```
Yard = fscanf(fid, '%*s %*southward\n%*due south %*s %*s %*southward\nM=%d\n\n', one);            
```
By default, fscanf reads data according to our format clarification until information technology does not observe any match for the data, or information technology reaches the end of the file. Here we will apply for loop for reading 3 sets of data and each time, it will read seven rows and 5 columns.
We will create a structure named mydata in the workspace to store information read from the file. This structure has three fields - fourth dimension, calendar month, and raindata array.

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

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

When you lot run the file, information technology displays the post-obit result −

12:00:00 June-2012    17.2100   17.5700   11.0900   xiii.1700   14.4500    28.5200       NaN    nine.5900       NaN   fourteen.0000    39.7800   12.0100    9.3300   14.8900   18.2300    16.5500   17.9200       NaN   xix.3300   10.3400    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    14.3800   nineteen.3300   xxx.3400   34.8900   28.6700    11.8600   thirty.9700   27.9500   29.3300   xxx.3400    16.8900   49.5000   xvi.4600   30.9700   27.9500    twenty.4600   47.6500   19.3400   49.5000   36.4600    23.1700   24.4500   30.4600   47.6500   29.3400  15:03:twoscore August-2012    17.0900   xiii.4800   27.2100   11.4500   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    19.2200   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   xviii.6700