Why is MatLab outputting 0s instead of the value?

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Jenah
Jenah 2022-9-17
评论： Torsten 2022-9-17
I am trying to create a matrix of an equation, E2, evaluated at different values of x (in a matrix). Why is it outputting 0s in the E2 matrix, but when I evaluate the equation at a certain element of the x matrix individually, it can print it just fine?
>> format long
>> x
x =
0.100000000000000
0.010000000000000
0.001000000000000
0.000100000000000
0.000010000000000
0.000001000000000
0.000000100000000
0.000000010000000
0.000000001000000
0.000000000100000
0.000000000010000
0.000000000001000
0.000000000000100
0.000000000000010
>> E2 = (-1/(1+sec(x)))'
% here it seems that E2 is only printing first element of x array
E2 =
-0.498747913711429
0
0
0
0
0
0
0
0
0
0
0
0
0
% however, when I evaluate at different elements of the matrix seperately,
% it can print it... see...
>> E2 = (-1/(1+sec(x(2))))'
E2 =
-0.499987499791664
>> E2 = (-1/(1+sec(x(7))))'
E2 =
-0.499999999999999

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采纳的回答

Torsten
Torsten 2022-9-17
E2 = (-1./(1+sec(x)))'
instead of
E2 = (-1/(1+sec(x)))'
  2 个评论
Jenah
Jenah 2022-9-17
Thank you! That worked. Okay, but I also have E1 which isn't printing out all the values of the matrix. Do I need to adjust anything here?
E1 = ((1-sec(x))./(tan(x).^2))'
Torsten
Torsten 2022-9-17
Yes.
If x is a vector and you want to *, / or ^ expressions f1(x) and f2(x) that depend on x, you must use elementwise multiplication, division and potentiation:
f1(x).*f2(x), f1(x)./f2(x), f1(x).^f2(x).

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