xlim not working in 'loop' plots..

a=[1 2 3]; %input
for i =1 :1:3
    b=a.*3;
    c=a.*10;
end

subplot(1,4,1)
for i=1:3
    plot(a,b);
end
xlim=([1 30])

subplot(1,4,2:4)
for i=1:3
    plot(a,c);
end
xlim=([1 100]) 

[Jan]

Whenever you mention in the forum, that there is a problem, take the time to describe, what the problem is. "Is not working" is too lean. Explain the difference between the wanted and the obtained result or post a copy of the complete error message. This will increase your chances to get a useful answer fast.

[Cem Menlikli]

I really appreciate your tips. this is very helpful.. thought of simplifiying the code to explain the problem will help.. origonal code is a matrix eigenvalue problem and hence the multiplication.. was thinking it is something to do with indexed subplot function.. a good example when you are tird, you should stop and re-look at it next morning..

Answer 1

[Jan]

You do not call the function xlim() at all, but create a variable with the same name. Replace:

xlim=([1 100]) 

by

xlim([1 100])

without the = operator, which assigns a value to a variable.

The code contains several other problems:

a=[1 2 3]; %input
for i =1 :1:3
    b=a.*3;
    c=a.*10;
end

This executes the same assignments 3 times. The body of the loop does not depend on the loop counter, so you can omit the loop:

a = [1 2 3]; %input
b = a * 3;
c = a * 10;

Using the elementwise multiplication .* is not a problem here, but for multiplications with scalar the * operator is fine also.

subplot(1, 4, 1)
for i = 1:3
    plot(a, b);
end
xlim([1 30])   % Without =, see above

This plots the same line 3 times. If there was no hold('on') command before, plot() removes all formerly drawn objext from the axes. So this is just a waste of time.

subplot(1, 4, 2:4)
for i = 1:3
    plot(a, c);
end
xlim([1 100])

Same problem as above: The loop is useless.

Read the documentation of the for command again: for .

Note that there is a method, to define the XLimits using an assignment instead of a function:

AxesH      = axes;  % Or: AxesH = subplot(1, 4, 1), which replies the axes' handle also
AxesH.XLim = [1, 100];

Now XLim is not a variable, but a property of the Axes object.

Summary:

a = [1, 2, 3];
b = a * 3;
c = a * 10;

subplot(1, 4, 1);
plot(a, b);
xlim([1, 30]);
subplot(1, 4, 2:4);
plot(a, c);
xlim([1, 100]);

The readability of code is increased, if you insert spaces around operators. Writing vectors without separators saves some milliseconds during typing, but can cost hours for debugging. See:

[1 0]
[1+ 0]
[1 + 0]
[1 +0]

With commas as separators, the result does not not depend on blanks anymore and this is a good programming practice.