How to plot for a loop

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Ender Rencuzogullari 2018-5-7

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评论： Ender Rencuzogullari 2018-5-7

Hi Everybody, I need to get plot of this loop, below, in an one plot. However, I am having an empty plot. How can I solve this problem? I mean that I need delta_V value for every value of 1000 on x axis. Thanks in advance.

Edit: It is surprising that when I run this script a few more times, It worked. So, why did that happen? Can you please explain?

E = 15000;
delta_p = 1000;
Vo = 7.854 ;
for i = 1:10
delta_V(i) = delta_p * Vo / E;
Vo = Vo - delta_V(i);
end
figure
plot(1000:1000:10000,delta_V)
title('Compression Ratio')
xlabel('Pressure Change')
ylabel('Volume Change')
hold on

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Answer 1

sloppydisk 2018-5-7

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编辑：sloppydisk 2018-5-7

在 MATLAB Online 中打开

This should work just fine, although I would suggest using

figure(1)

instead of

figure

, which makes a new figure on every run. This is probably what caused you to see an empty figure at some point.

Also for good practice preallocate delta_V before the for loop:

V = zeros(1, 10);

And you don't need the hold on in this case, because you aren't plotting multiple lines in one figure.

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sloppydisk 2018-5-7

编辑：sloppydisk 2018-5-7

Probably because this is a very small loop so it is not really necessary, but I would still do it to get used to it. Here the time gained by not dynamically expanding the array is apparently smaller than the time lost by preallocating. Try increasing the number of elements to 10000, then you should see it being a lot faster.

Ender Rencuzogullari 2018-5-7