Very basic calculations returning incorrect values
显示 更早的评论
So I'm trying to run some very, very basic equations through Matlab, and I'm getting absurd values for some reason. Here is a sample of the code I'm trying to run:
r1 = 0.1;
r2 = 0.12;
r3 = 0.14;
h1 = 0.200;
h2 = 0.240;
x = r2-r1;
A1 = pi*square(r2) ;
V1 = pi*square(r1)*h1 ;
V2 = pi*square(r2)*h2 ;
Vt = V2-V1 ;
V3 = pi*square(r3)*h2 ;
Vi = V3-V2;
However the value returned by Matlab for A1 is 3.1416, when it should be more like 0.045. The same thing happens for V1, V2, and V3. Also for some reason, the values returned for V2 and V3 are both 0.754, which is kind of odd. I'm very new to this and I'm sure I'm just making some silly mistake. Any help would be appreciated.
1 个评论
or simply x.*x
采纳的回答
Of course the results are exactly, what they are expected to be. I assume, you expectations to the function square are wrong. Please read the documentation: doc square.
r2 = 0.12;
square(r2)
% >> 1
A1 = pi*square(r2)
% A1: 3.14159265
square does not the square the value of the argument. I guess you mean:
A1 = pi * r2 ^ 2
This replies 0.0452 .
2 个评论
Oliver Green
2018-2-5
John D'Errico
2018-2-5
Well, you were not entirely to blame. I'd say that it is easy to presume square is a function that squares a number. It makes perfect sense to me.
The learning point is to not assume you know what a function does without reading the help for that function. Look at the examples provided, etc. For example, a common mistake that people make is that sin(30) should return 1/2. Of course that fails, since sin uses arguments in radians, not degrees. So always read the help for tools that you will use. It will save you a great deal of debugging time in the long run.
更多回答（1 个）
Use x^2 instead of square(x) (square is not what you expect it to be in MATLAB).
Best wishes
Torsten.
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