How do get past the first interation in this nested loop?

old=Rod_Temp_Gradient;
new=zeros(size(Rod_Temp_Gradient));
count=0;
while max(new)- min(new)<0.5
    for col=length(old)
        new=[mean(old(1:2)),  conv(old,[1,1,1]/3,'valid'),   mean(old(end-1:end))];
    end
    old=new;
    count=count+1;
end

[Rik]

If you correctly format your question (select you code and hit the {}Code button) and mention the error (all the text in red), we can help you much more easily.

[KALYAN ACHARJYA]

Pls, clarify Past or Pass?

[Josh Neff]

old=Rod_Temp_Gradient;
new=zeros(size(Rod_Temp_Gradient));
count=0;
while max(new)- min(new)<0.5
    for col=1:length(old)
        new=[mean(old(1:2)),  conv(old,[1,1,1]/3,'valid'),   mean(old(end-1:end))];
    end
    old=new;
    count=count+1;
end

I do not receive any errors, but I can look at the vector and see the max and min are not within 0.5 of each other and it won't preform past the first iteration. It needs to preform several until equilibrium is reach in the heat distribution in a 1 d array rod or until the max and min are within range. it won't keep going, it stops after the first iteration.

[Josh Neff]

It doesn't make it to iteration 2, 3, 4, .....

[Jan]

Please do not explain, what the computer does not do, but what it does do instead.

[Rik]

Can you share an example of Rod_Temp_Gradient so we can run this code to see what happens?

[Josh Neff]

100  96.0789439152323  92.3116346386636  88.6920436717158  85.2143788966211  81.8730753077982  78.6627861066553  75.5783741455726  72.6149037073691  69.7676326071031  67.0320046035639  64.4036421083141  61.8783391806141  59.4520547970194  57.1209063848815  54.8811636094027  52.7292424043049  50.6616992365590  48.6752255959972  46.7666427009909  44.9328964117222  43.1710523429080  41.4782911681581  39.8519041084514  38.2892885975112  36.7879441171442

[Matt J]

I just wanted to point out that putting the line

new=[mean(old(1:2)),  conv(old,[1,1,1]/3,'valid'),   mean(old(end-1:end))];

inside the following for-loop makes no sense. The loop is just repeating the exact same calculation multiple times.

    for col=1:length(old)
        new=[mean(old(1:2)),  conv(old,[1,1,1]/3,'valid'),   mean(old(end-1:end))];
    end

Answer 1

[Rik]

The problem lies with your condition in the while command. It keeps executing while some statement is true, not until some statement is true. The problem is that you initialize new with only zeros, so the first iteration the condition is true, as max-min is 0.

Rod_Temp_Gradient=[100  96.0789439152323  92.3116346386636  88.6920436717158  85.2143788966211  81.8730753077982  78.6627861066553  75.5783741455726  72.6149037073691  69.7676326071031  67.0320046035639  64.4036421083141  61.8783391806141  59.4520547970194  57.1209063848815  54.8811636094027  52.7292424043049  50.6616992365590  48.6752255959972  46.7666427009909  44.9328964117222  43.1710523429080  41.4782911681581  39.8519041084514  38.2892885975112  36.7879441171442];
old=Rod_Temp_Gradient;
new=zeros(size(Rod_Temp_Gradient));
count=0;
while (max(new)- min(new))>0.5 || count==0
    for col=length(old)
        new=[mean(old(1:2)),  conv(old,[1,1,1]/3,'valid'),   mean(old(end-1:end))];
    end
    old=new;
    count=count+1;
end

The trick is to force the first run with count==0 and then have the inversion of your original statement.

Answer 2

[Jan]

Use the debugger to step through your code line by line: https://www.mathworks.com/help/matlab/matlab_prog/debugging-process-and-features.html. This allows you to examine, what's going on in which command.