Page 45 - Applied Statistics Using SPSS, STATISTICA, MATLAB and R

24 1 Introduction

>> c(1,2)={‘T80’};
>> c(1,3)={‘T82’};
>> c
c =
‘Pmax’ ‘T80’ ‘T82’

The first command uses function cell to define a cell array with 1×3 objects.
These are afterwards assigned some string values (delimited with ‘). When
printing the c values one gets the confirmation that c is a row vector with the three
strings (e.g., c(1,2) is ‘T80’).
When specifying matrices in MATLAB one may use comma to separate column
values and semicolon to separate row values as in:

» x=[1, 2 ; 3, 4];

Matrices can also be used to define other matrices. Thus, the previous matrix x
could also be defined as:

» x=[[1 2] ; [3 4]];
» x=[[1; 3], [2; 4]];

One can confirm that the matrix has been defined as intended, by typing x after
the prompt, and obtaining:

x =
1 2
3 4
The same result could be obtained by removing the semicolon terminating the
previous command. In MATLAB a semicolon inhibits the production of screen
output. Also MATLAB commands can either be used in a procedure-like manner,
producing output (as “answers”, denoted ans), or in a function-like manner
producing a value assigned to a variable (considered to be a matrix). This is
illustrated next, with the command that computes the mean of a sequence of values
structured as a row vector:

» v=[1 2 3 4 5 6];
» mean(v)
ans =
3.5000
» y=mean(v)
y =
3.5000

Whenever needed one may know which objects (e.g. matrices) are currently in
the console environment by issuing who . Object removal is performed by writing
clear followed by the name of the object. For instance, clear x removes
matrix x from the environment; it will no longer be available. The use of clea r
without arguments removes all objects from the environment.