Math245 Computer Lab set #4, Spring 2009
1
The for loop
The
for
loop is a Matlab construct that repeats block of statements for specified number of times. The
for
loop has the form:
for index = expression;
statement 1;
...
statement n;
end
This
for
loop executes Matlab statements 1 to n for all values of the loop variable
index
specified by the
expression
. For example,
for i=1:10;
statement 1;
...
statement n;
end
This
for
loop repeats statement 1 to n from
i=1
to
i=10
. At the first time, Matlab assigns
i=1
, then the
statement block is executed. When Matlab hits
end
line Matlab goes back to
for
line assigning
i=2
, and
statement block is executed. Matlab repeats this process up to
i=10
. In this example, if the expression for
index variable is
i=0:2:10;
, the statement block is repeated from
i=0
to
i=10
, step 2(
i=0,2,4,...,10
).
Here is an example to calculate 100!.
fact=1;
for i=1:100;
i
fact = fact*i
pause;
end
Here is an example to calculate a geometric sum
50
X
i
=0
ar
i
=
a
+
ar
+
ar
2
+
ar
3
+
· · ·
with
a
= 2 and
r
= 0
.
5.
n=50;
a=2;
r=0.5;
gsum=a;
for i=1:n;
gsum=gsum+a*r^i;
end
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 Spring '07
 Alexander
 Math, matlab, parameter values, main program

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