How To Import Data Into Matlab

MATLAB - Data Import

Importing information in MATLAB means loading data from an external file. The importdata role allows loading various information files of dissimilar formats. It has the following five forms −

Sr.No.	Part & Description
ane	A = importdata(filename) Loads data 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 as the column separator in ASCII file, filename, or the clipboard information. You can use delimiterIn with any of the input arguments in the in a higher place syntaxes.
4	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 character for the input ASCII file in delimiterOut and the detected number of header lines in headerlinesOut, using whatsoever of the input arguments in the previous syntaxes.

By default, Octave does not have support for importdata() function, then you will take to search and install this package to brand following examples work with your Octave installation.

Example 1

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

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

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

Importing Imange Files

Example 2

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

Our text file weeklydata.txt looks like this −

Sunday  MonDay  TuesDay  WednesDay  ThursDay  FriDay  Sabbatum 95.01   76.21   61.54    40.57       55.79    70.28   81.53 73.11   45.65   79.19    93.55       75.29    69.87   74.68 60.68   41.85   92.18    91.69       81.32    90.38   74.51 48.sixty   82.fourteen   73.82    41.03       0.99     67.22   93.eighteen 89.13   44.47   57.63    89.36       13.89    nineteen.88   46.60

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

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

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

Dominicus    95.0100    73.1100    60.6800    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    twoscore.5700    93.5500    91.6900    41.0300    89.3600   Thursday    55.7900    75.2900    81.3200    0.9900    13.8900   Fri    70.2800    69.8700    90.3800    67.2200    xix.8800  Sabbatum    81.5300    74.6800    74.5100    93.1800    46.6000

Example 3

In this example, let us import information from clipboard.

Re-create the following lines to the clipboard −

Mathematics is unproblematic

Create a script file and type the following code −

A = importdata('-pastespecial')

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

A =     'Mathematics is simple'

Low-Level File I/O

The importdata function is a loftier-level function. The depression-level file I/O functions in MATLAB allow the nearly control over reading or writing data to a file. Withal, these functions demand more detailed data about your file to work efficiently.

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

Function	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 near open files
fprintf	Write data to text file
fread	Read information from binary file
frewind	Move file position indicator to beginning of open file
fscanf	Read data from text file
fseek	Movement 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 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 ane line of a file at a time, where a newline character separates each line.
The fread role reads a stream of data at the byte or bit level.

Case

Nosotros have a text data file 'myfile.txt' saved in our working directory. The file stores rainfall data for three months; June, July and Baronial for the year 2012.

The information in myfile.txt contains repeated sets of time, month and rainfall measurements at five places. The header data stores the number of months M; so we have Thousand 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  xvi.55 23.67 19.15  0.35   17.57  NaN   12.01 17.92  28.49  17.xl  17.06 11.09 nine.59   nine.33   NaN    0.31  0.23  ten.46  13.17  NaN    14.89 19.33 20.97  nineteen.50  17.65  xiv.45 14.00 18.23  10.34  17.95  16.46 nineteen.34 09:10:02 July-2012 12.76  16.94  fourteen.38  11.86 xvi.89 xx.46  23.17  NaN    24.89 19.33 xxx.97  49.l  47.65  24.45 34.00 18.23  thirty.34  27.95  16.46 19.34 thirty.46  33.17  NaN    34.89  29.33 30.97  49.50  47.65  24.45 34.00 28.67  30.34  27.95  36.46 29.34 15:03:forty August-2012 17.09  16.55  19.59  17.25 19.22 17.54  xi.45  xiii.48  22.55 24.01 NaN    21.nineteen  25.85  25.05 27.21 26.79  24.98  12.23  16.99 xviii.67 17.54  11.45  xiii.48  22.55 24.01 NaN    21.19  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 post-obit steps −

Open up the file with fopen function and get the file identifier.
Depict the data in the file with format specifiers, such equally '%due south' 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 render the unmarried value for One thousand, nosotros write −
```
1000 = fscanf(fid, '%*s %*south\n%*s %*southward %*s %*s\nM=%d\n\north', 1);            
```
By default, fscanf reads information co-ordinate to our format description until it does not find any lucifer for the data, or it reaches the end of the file. Here we will utilize for loop for reading 3 sets of data and each fourth dimension, it will read 7 rows and 5 columns.
We volition create a construction named mydata in the workspace to store data read from the file. This structure 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 = five;   % open the file fid = fopen(filename);   % read the file headers, notice Yard (number of months) M = fscanf(fid, '%*southward %*s\n%*s %*s %*south %*s\nM=%d\northward\north', ane);   % read each ready of measurements for n = 1:M    mydata(n).fourth dimension = fscanf(fid, '%s', one);    mydata(n).month = fscanf(fid, '%s', 1);      % fscanf fills the array in column order,    % then transpose the results    mydata(northward).raindata  = ...       fscanf(fid, '%f', [rows, cols]); end for due north = 1:M    disp(mydata(due north).fourth dimension), disp(mydata(n).month)    disp(mydata(n).raindata) cease   % close the file fclose(fid);

When you run the file, it displays the post-obit result −

12:00:00 June-2012    17.2100   17.5700   11.0900   13.1700   xiv.4500    28.5200       NaN    9.5900       NaN   14.0000    39.7800   12.0100    9.3300   14.8900   18.2300    sixteen.5500   17.9200       NaN   nineteen.3300   10.3400    23.6700   28.4900    0.3100   20.9700   17.9500    xix.1500   17.4000    0.2300   19.5000   16.4600    0.3500   17.0600   10.4600   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   19.3300   30.3400   34.8900   28.6700    11.8600   30.9700   27.9500   29.3300   30.3400    16.8900   49.5000   16.4600   30.9700   27.9500    twenty.4600   47.6500   19.3400   49.5000   36.4600    23.1700   24.4500   30.4600   47.6500   29.3400  xv:03:forty August-2012    17.0900   thirteen.4800   27.2100   11.4500   25.0500    16.5500   22.5500   26.7900   13.4800   27.2100    xix.5900   24.0100   24.9800   22.5500   26.7900    17.2500       NaN   12.2300   24.0100   24.9800    19.2200   21.1900   xvi.9900       NaN   12.2300    17.5400   25.8500   18.6700   21.1900   xvi.9900    11.4500   25.0500   17.5400   25.8500   18.6700