Calculating values of a dependent variable at a using a range of independent variables

Hi,

I'm new to matlab so this might be very simple but....

I have this equation;

Eff=((Cv.*Temp.*(1-Vr))+(((2.*l.*S.*S)./(n.*n))*((Vi./(pi.*Rb.*Rb))-l))+(M./(R.*Temp))+((Vr^(1-k)).*(R.*Temp./M)))/((Cv.*Temp)+((R.*Temp)./M)+(((S.*Vi)./(sqrt(2).*n.*pi.*Rb.*Rb))^2))

All of the variables are constants except Eff and Temp. I would like to calculate values of Eff using Temp between a range of 373 and 623 so that I can plot a graph to investigate the effect of Temp on Eff.

Any Advice would be greatly appreciated

Answer 1

[Chad Greene]

Welcome to the world of Matlab, Tom.

Indeed, I think this is pretty straightforward. To make a range of values of Temp between 373 and 623, do

Temp = 373:623;

Alternatively, to do the same thing but in steps of 0.1, do

Temp = 373:0.1:623;

Then calculate Eff by

Eff=((Cv.*Temp.*(1-Vr))+(((2.*l.*S.*S)./(n.*n))*((Vi./(pi.*Rb.*Rb))-l))+(M./(R.*Temp))+((Vr^(1-k)).*(R.*Temp./M)))/((Cv.*Temp)+((R.*Temp)./M)+(((S.*Vi)./(sqrt(2).*n.*pi.*Rb.*Rb))^2));

and plot the results like this:

plot(Temp,Eff) 

[Chad Greene]

...That's assuming you've already defined all the constants with a series of lines like

Rb=5; 
Vi=6; 
S=7; 
Vr=8; 

...etc

[Tom Morris]

Hi Chad,

Thanks for responding so quickly!

I have tried this and it only produces a single answer for Eff and when I plot the graph it is blank (I'm assuming that is because you can't plot a line for a single point)

I have attached a photo

[Chad Greene]

Ahh, try this. It looks like a few dot operators were missing. My go-to solution when things are acting funny with multiplication, division, or exponents, is to put a dot in front of each one. That seems to have fixed it.

Eff=((Cv.*Temp.*(1-Vr))+(((2.*l.*S.*S)./(n.*n)).*((Vi./(pi.*Rb.*Rb))-l))+(M./(R.*Temp))+((Vr.^(1-k)).*(R.*Temp./M)))./((Cv.*Temp)+((R.*Temp)./M)+(((S.*Vi)./(sqrt(2).*n.*pi.*Rb.*Rb)).^2));

[Tom Morris]

That's got it! Thank you so much for your help, I was going a bit crazy there.