Matrix calculation(replacing a new value instead of matrix element)

Question

shirin mhd 2022-3-31

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1685384-matrix-calculation-replacing-a-new-value-instead-of-matrix-element

评论： Voss 2022-3-31

Hi everyone

I've written this code. my purpose is to make a matrix(1*3), which each element (T1,T2,T3) of that is calculated in upper lines. But it doesn't work. what should i do?

a1=7;
a2=12;
a3=4;
w1=min([a1,a2,a3]);
f1=double(a1-w1);
f2=double(a2-w1);
f3=double(a3-w1);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if f1==0
    final=w1;
    T1=-10e10;
else
T1=f1;
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if f2==0
    final=w1;
    T2=-10e10;
else
T2=f2;
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if f3==0
    final=w1;
    T3=-10e10;
else
T3=f3;
end
T=[T1,T2,T3]

i expect after run T becomes [3 8 -10e10]

but what code does is:

T =
   1.0e+11 *
    0.0000    0.0000   -1.0000

in other word, I want replace some elements in a matrix with new calculated value during some steps.which part is wrong?

I appreciate any help.

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Answer 1

the cyclist 2022-3-31

1
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https://ww2.mathworks.cn/matlabcentral/answers/1685384-matrix-calculation-replacing-a-new-value-instead-of-matrix-element#answer_931464

在 MATLAB Online 中打开

The code is doing what you expect, but the format of the output obscures the result. Try using format long, and you'll see the result more clearly:

a1=7;
a2=12;
a3=4;
w1=min([a1,a2,a3]);
f1=double(a1-w1);
f2=double(a2-w1);
f3=double(a3-w1);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if f1==0
    final=w1;
    T1=-10e10;
else
T1=f1;
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if f2==0
    final=w1;
    T2=-10e10;
else
T2=f2;
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if f3==0
    final=w1;
    T3=-10e10;
else
T3=f3;
end
format long
T=[T1,T2,T3]
T = 1×3
1.0e+11 *

   0.000000000030000   0.000000000080000  -1.000000000000000
T1
T1 = 
     3
T2
T2 = 
     8
T3
T3 = 
    -1.000000000000000e+11

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shirin mhd 2022-3-31

Thank you for your help and attention. I really appreciate your kindness.

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Answer 2

Voss 2022-3-31

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1685384-matrix-calculation-replacing-a-new-value-instead-of-matrix-element#answer_931469

在 MATLAB Online 中打开

The result T you get is correct. The confusion is because of how T is displayed in the Command Window. You can look at one element at a time to see them, or you can change how numbers are displayed in the Command Window:

Looking at individual elements of T:

T = [3 8 -10e10] % shows all of T, as-is
T = 1×3
1.0e+11 *

    0.0000    0.0000   -1.0000
T(1)
ans = 3
T(2)
ans = 8
T(3)
ans = -1.0000e+11

Changing the Command WIndow format:

format long
T
T = 1×3
1.0e+11 *

   0.000000000030000   0.000000000080000  -1.000000000000000

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shirin mhd 2022-3-31

Thank you for your help and attention. I really appreciate your kindness.

Voss 2022-3-31

You're welcome!

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Answer 3

Image Analyst 2022-3-31

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1685384-matrix-calculation-replacing-a-new-value-instead-of-matrix-element#answer_931474

在 MATLAB Online 中打开

Those are the values. It's just that when using 1e11 as the base, the 3 and 8 don't show in the display. To solve that put this at the top of your code

format long g