.mlx files: Live Code File Format. This format were just introduced on MATLAB version R2016a. This type of files storing the live scripts/live functions that uses the Live Code file format.

Import functions

The function that usually are used to import data into MATLAB : importdata(filename)
importdata(filename) can loads data into array.

 % sample script of loading an images
 >> A = importdata('example1.png');
 imread(A)

Loading Data

load(filename) can loads data from filename. The files can be text, images , and even audio files.

 % sample script of loading an audio
 >> B = load('example2.mp3');
 audioread(B,single,1.0)

The load command is used to load data from a file into the current workspace.

Load all variables from the file mySave.mat into the current workspace.

 >> load('mySave.mat')
 >> load(fullfile(pwd, 'mySave.mat'))

Load just the variables myData1 and myData2.

 >> load('mySave.mat', 'myData1', 'myData2')

Load all myData variables.

 >> load('mySave.mat', 'myData*')

Get a cell array of variables in saved file.

 >> whos('-file', 'mySave.mat')

Saving Data

The save command is used to save workspace data to a file.

Save all workspace data to the file mySave.mat in the current directory.

 >> save('mySave.mat')
 >> save(fullfile(pwd, 'mySave.mat'))

Save just the variables myData1 and myData2 to mySave.mat.

 >> save('mySave.mat', 'myData1', 'myData2')

Save all myData variables to mySave.mat.

 >> save('mySave.mat', 'myData*')

Save all myData variables to a mySave.mat file compatible with version 6 of MATLAB.

 >> save('mySave.mat', 'myData*', '-v6')

Save all myData variables to an ASCII file.

 >> save('mySave.mat', 'myData*', '-ASCII')

Append new variables to the data file.

 >> save('mySave.mat', 'newData*', '-append')

Excel Spreadsheets I/O

Since analyzing data is one of the more common motivations for using input output I will start with reading and writing from a spreadsheet. I cover the command line first since it is often necessary to import the data while an m-function is being evaluated.

Reading Excel Spreadsheets

MATLAB makes it easy to read from an Excel spreadsheet. It has the built-n command readcell

Let say, you have an Excel file (Preferably latest version with file format .xlsx ) , In this example, you have a table with data shown as below saved as Class Marks.xlsx in any place of your liking


Name	Marks
Ali	93
Chin	47
Sammy	74
Dorothy	96
Huat	94
Anna	38

To read the contents , you need to type as follows:

A=readcell('C:\mydir\Class Marks.xlsx') % mydir is referring where you actually saves the Excel file

Pro tips: If you are unsure of the file location, right click of the file that you saved and select Properties and look for Locations in General tabs. You can change mydir into your selected locations

It will shows the output as follows

A =

  7×2 cell array

    {'Name'   }    {'Marks'}
    {'Ali'    }    {[   93]}
    {'Chin'   }    {[   47]}
    {'Sammy'  }    {[   74]}
    {'Dorothy'}    {[   96]}
    {'Huat'   }    {[   94]}
    {'Anna'   }    {[   38]}

This line of code reads Class Marks.xlsx (from the saved directory - mydir) and places it in an identical array inside MATLAB called A. You can then manipulate the array A in any way you want.

Reading from certain range in the text files

From table above just now, we expand to more rows and columns as shown below in Sheet named Class1A. Note that A-> H and 1->11 are for references

In this example, we are interested , we interested in Huat marks and make an array B to extract his marks

	A	B	C	D	E	F	G	H
1	Name	English	Maths	Science	Art	Music	Malay	Moral
2	Ali	71	54	65	27	65	54	96
3	Chan	14	96	50	40	17	99	95
4	Sammy	17	15	72	24	55	15	26
5	Dorothy	89	35	45	14	87	52	65
6	Huat	82	90	15	65	42	82	90
7	Anna	12	77	25	63	46	14	31
8	Lee	77	22	49	91	43	89	66
9	Muthu	61	25	38	65	43	35	89
10	Ismail	70	70	79	75	81	44	98
11	Th'ng	42	92	99	14	46	12	24

The comments explained how to select certain range of wanted data.

B=readcell('C:\mydir\Class Marks.xlsx','Sheet','Class1A','Range','A6:H6') 
%mydir is the location where Excel is stored
%sheet is to select which sheet
%range can be selected with following manner
%a. form 'A1' (cell)
%b. form 'A:B' (column-select)
%c. form '1:5'(row-select)
%d. form 'A1:B5' (rectangle-select)

The B array will show following results

B =

  1×8 cell array

    {'Huat'}    {[82]}    {[90]}    {[15]}    {[65]}    {[42]}    {[82]}    {[90]}

Writing Excel Spreadsheets

The writecell command allows data to be added into the Excel files.

First, we create data for our student Juan.as followed:

B = {'Juan' , 43,67,88,45,35,92,65} % create a row matrix

B =

  1×8 cell array
    {'Juan'}    {[43]}    {[67]}    {[88]}    {[45]}    {[35]}    {[92]}    {[65]}

Later on , use the writecell command (Make sure the Excel file is closed to prevent error message following)

Error using writecell (line 149)
Unable to write to file 'C:\mydir\Class Marks.xlsx'.  You may not have write permissions or the file may be open by another application.

writecell(B,'C:\mydir\Class Marks.xlsx','Sheet','Class1A','Range','A12');
%mydir is location where the excel file is located
%sheet is Class1A
%range is starting cell where to paste the data

When you open back the Excel files: you should see Juan with his marks

	A	B	C	D	E	F	G	H
1	Name	English	Maths	Science	Art	Music	Malay	Moral
2	Ali	71	54	65	27	65	54	96
3	Chan	14	96	50	40	17	99	95
4	Sammy	17	15	72	24	55	15	26
5	Dorothy	89	35	45	14	87	52	65
6	Huat	82	90	15	65	42	82	90
7	Anna	12	77	25	63	46	14	31
8	Lee	77	22	49	91	43	89	66
9	Muthu	61	25	38	65	43	35	89
10	Ismail	70	70	79	75	81	44	98
11	Th'ng	42	92	99	14	46	12	24
12	Juan	43	67	88	45	35	92	65

Text files I/O

Reading Text Files

If a file is not an excel spreadsheet, it can still be read using "load" function:

>> load newfile.txt

This works only if the text is entirely numerical, without special formatting. Otherwise you get an 'unrecognized character' error.

The easiest way to write to a non-excel file, or using MATLAB 6.5 or less, is to use the same code as that for writing excel files but change the extension. Usually there are no formatting difficulties with plain text files.

For reading more general text files, MATLAB does not have a function to do it easily (unless you have excel), but you can read very general text files (with different delimiters for both cells and text within cells) using the "textread.m" function in the MATLAB file exchange (do a google search to find it). You can also try to use fscanf if the formatting is consistent enough (i.e. consistent numbers of spaces, no mixing of strings and numbers in columns, and so on).

MATLAB File I/O: from the Graphical User Interface

MATLAB contains a nice GUI application that will guide you through importing data from any recognized data file (usually .mat, .txt, or .xls on a Windows system). To use it, go to file > import data, and select the file you want. Then, choose what column separators are present (by selecting the appropriate radio button). Finally, click "next".

MATLAB saves the variable under a name similar to that of the file, but with modifications to make it conform with MATLAB syntax. Spaces are omitted, plusses and minuses are turned into other characters. To see the name MATLAB generated (and probably change it) type "who" in the command prompt.

External Resources

ControlTheoryPro.com

MatlabCodes.Webs.com

MATLAB Programming/Basic Reading and Writing data from a file

Contents

MATLAB file types