MATLAB - The Language of Technical Computing

MATLAB Programming

Basic MATLAB Concepts

Saving and loading a MAT-file

file > set path... > add folder...

save filename.mat or

save filename.fig 

• save - saves data to files, *.mat by default
• uisave - includes user interface
• hgsave - saves figures to files, *.fig by default
• diary [filename] - saves all the text input in the command window to a text file

 One way is to use the "file" menu. To open a .m file click "open", whereas to import data from a data file select "import data..." and follow the wizard's instructions.

To open an .m file, you can use file -> open, or type

 

>>open filename.mat

MATLAB Command Prompt

Calculator

>> 3503-3215
ans =
   288

>> 288/10
ans =
   28.8

>> 28.8 * 15.4
ans =
  443.5200

>> distance = 3503-3215 
distance = 
   288 
>> mileage = distance/10
mileage =
   28.8000 
>> projected_distance = mileage * 15.4
projected_distance =
  443.5200

 Reading and Writing data from/to a .mat file

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

>> 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')

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

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

Load all myData variables.

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

Get a cell array of variables in saved file.

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

MATLAB makes it easy to read from an Excel spreadsheet. 

It has the built in command "xlsread". To use the xlsread function 

use the syntax:

>>g=xlsread('filename');

To write data to an .xls the procedure is very similar. The xlswrite command below 

creates a spreadsheet called filename.xls in the current directory from 

the variable g: 

>> xlswrite('filename',g);

Reading and Writing from and to other text files

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

Declaring Strings

Besides numbers, MATLAB can also manipulate strings. 

They should be enclosed in single quotes:

>> fstring = 'hello'
 fstring =
 hello

>> fstring = 'you''re'
 fstring =
 you're

An important thing to remember about strings is that MATLAB treats them 
as array of characters. To see this, try executing the following code:

>> fstring = 'hello';
 >> class(fstring)
 ans = char

Attempting to perform arithmetic operations on character arrays 

converts them into doubles.  

>> fstring2 = 'world';
 >> fstring + fstring2
 ans = 223   212   222   216   211

These values are obtained by using the 'double' function to turn the 

array into an array of doubles.  

>> double(fstring)
 ans = 104   101   108   108   111

Displaying values of string variables

>> fstring = 'hello';
 >> display( [ fstring 'world'] )
 helloworld

  >> fstring = ['you' char(39) 're']
 fstring = you're

>> strCell = {'A', 'B'};
 >> strcat(strCell, '_');
 ans =
 A_
 B_

>> X = 9.2
 >> fprintf(1, '%1.3f\n', X);
 9.200

>> X = 9.2
 >> fprintf(1, 'The value of X is %1.3f meters per second \n', X);
 The value of X is 9.200 meters per second

>> strCell = {'Aa', 'AA'};
 >> strmatch('A', strCell);
 ans = 1, 2
 >> strmatch('A', strCell, 'exact');
 ans = []
 >> strmatch('Aa', strCell, 'exact');
 ans = 1

>> strCell = {'Aa', 'AA'};
 >> strfind(strCell, 'A');
 ans = % answer is a cell array with two elements (same size as strCell): 
   1         % Index of the beginning of string "A" in the first cell
   1  2      % Index of each instance of the beginning of string "A" in the second cell
 >> strfind(strCell, 'a');
 ans =
   2
   [] % 'a' is not found

>> string1 = 'a';
 >> strcmp(string1, 'a')
 ans = 1
 >> strcmp(string1, 'A')
 ans = 0