How to find matrix dimensions while using * operator ?

Question

Sai Charan 2017-2-16

回答： Roger Stafford 2017-2-16

i was trying to plot this equation Nw=10(50+(7.5(w)1/2))+20log10(f)40log10(f+0.4))Nwoff, i got the below error.

f=200:100:200000;

Nwoff=1:10;

for n=Nwoff

Nw=10.^((50+(7.5*1/2))+20*log10(f).^40*log10(f+0.4))*n;

plot(f,Nw)

hold on

end

Error using * Inner matrix dimensions must agree.

thank you in advance.

Answer 1

Roger Stafford 2017-2-16

Your error lies in the expression

20*log10(f).^40*log10(f+0.4)

Here you are using matrix multiplication on two thousand-element row vectors, and that is a no-no. Undoubtedly you meant

20*log10(f).^40.*log10(f+0.4)

with a dot before the asterisk sign.

Your plot will be filled with ten different thousand-point curves with this correction.