Matlab) how can I plot graphs of function with various input arguments?

Question

mfunction.m

function[P] = mfunction(v,M,R,T)
P=4*pi*(M/(2*pi*R*T)).^(3/2)*v.^2*exp((-M*(v.^2))/(2*R*T));
end

I want to make a graph. x would be v and the range is 1: 1200,

M = 0.032,R = 8.31, T= 300

and I want to plot y=mfunction(x)

and errors pop up. How can I draw a graph?

>>x=1:1200; >>y=mfunction(x,4,8,100); ??? Error using ==> mtimes Inner matrix dimensions must agree. Error in ==> mfunction at 2 P=4*pi*(M/(2*piRT)).^(3/2)*v.^2*exp((-M*(v.^2))/(2*R*T)); — Kang_HM
– Kang_HM, Commented Feb 28, 2014 at 6:29

laser · Accepted Answer · 2014-02-28 07:30:11Z

1

The problem lies at the middle multiplication

P=4*pi*(M/(2*pi*R*T)).^(3/2)*v.^2  *   exp((-M*(v.^2))/(2*R*T));
                                   ^

What you are doing is similar to doing

[1,2] * [1,2]

, which gives you the error "mtimes Inner matrix dimensions must agree", because it is multiplying a mx1 matrix to an mx1 matrix.

Depending on want you need, you can do one of the following:

>> [1,2] * [1,2]'  %inner product

ans =

     5

>> [1,2]' * [1,2]

ans =

     1     2
     2     4

>> [1,2] .* [1,2]  %element-wise product

ans =

     1     4

answered Feb 28, 2014 at 7:30

laser

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