For loop while saving data in matrix

Question

Navin 2014-2-11

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/115753-for-loop-while-saving-data-in-matrix

编辑： the cyclist 2014-2-11

Good day i'm quite new to mathlab and i'm having a bit of problems. I'm not new to programming but i am new to matlab and for some reason i can't get past this problem. Any help would be greatly appreciated. I am trying to have a for loop which starts at 1 and decriments by 0.01 and stops at 0.0001 in this loop i need values to be stored in an array for both variable, Tind and s. S changes in the loop and would be the same values as the loop itself which is from 1 to 0.0001 with a decriment of 0.01.. After storing both of these values in a matrix i would then plot them. Below is my code. I'm a bit new so my apologies if my code is a bit nooby.

        for k=[1:-0.01:0.0001]
    s(k)= k
    ws=1800*((2*pi)/60)
Vth=255.2
R2=.332
Rth=0.59
Xth=1.106
X2=0.464
a=1/ws
b=(3*Vth.^2*(R2/s))
c=((Rth+(R2/s)).^2+(Xth+X2).^2)
Tind(k)=a*(b/c)
end
Plot(Tind,s)

I get the following error

Attempted to access s(0.99); index must be a positive integer or logical.

Error in test (line 2) s(k)= k

Any help would be greatly appreciated. Thank You.

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Answer 1

the cyclist 2014-2-11

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/115753-for-loop-while-saving-data-in-matrix#answer_124016

编辑：the cyclist 2014-2-11

在 MATLAB Online 中打开

The main problem with your code is that you are trying to use a real-valued variable as an index, but indices have to be 1,2,3 ....

Here is some code that stays true to your looping structure:

Vth=255.2;
R2=.332;
Rth=0.59;
Xth=1.106;
X2=0.464;
ws = 1800*((2*pi)/60);
a = 1/ws;
kRange = 1:-0.01:0.0001;
numberOfK = numel(kRange);
for nk= 1:numberOfK
    s(nk) = kRange(nk);
    b = (3*Vth.^2*(R2/s(nk)));
    c = ((Rth+(R2/s(nk))).^2+(Xth+X2).^2);
    Tind(nk) = a*(b/c);
end
figure
plot(Tind,s)

Even better, though, is to take advantage of the fact that MATLAB is vectorized:

Vth=255.2;
R2=.332;
Rth=0.59;
Xth=1.106;
X2=0.464;
ws = 1800*((2*pi)/60);
a = 1/ws;  
s = 1:-0.01:0.0001;
b = (3*Vth.^2*(R2./s));
c = ((Rth+(R2./s)).^2+(Xth+X2).^2);
Tind = a*(b./c);
figure
plot(Tind,s)