Wednesday, August 5, 2009

for

Repeat statements a specific number of times

Syntax

  • for variable = expression
    statements
    end

Description

The general format is

  • for variable = expression
    statement
    ...
    statement
    end

The columns of the expression are stored one at a time in the variable while the following statements, up to the end, are executed.

In practice, the expression is almost always of the form scalar : scalar, in which case its columns are simply scalars.

The scope of the for statement is always terminated with a matching end.

Examples

Assume k has already been assigned a value. Create the Hilbert matrix, using zeros to preallocate the matrix to conserve memory:

  • a = zeros(k,k)  % Preallocate matrix
    for m = 1:k
    for n = 1:k
    a(m,n) = 1/(m+n -1);
    end
    end

Step s with increments of -0.1

  • for s = 1.0: -0.1: 0.0,..., end

Successively set e to the unit n-vectors:

  • for e = eye(n),..., end

The line

  • for V = A,..., end

has the same effect as

  • for k = 1:n, V = A(:,k);..., end

except k is also set here.


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