I want to use contourf function to plot 2d velocity data

I have the x,y and corersponding velocity components u and v as a matrix data. I want to use this matrix data to plot a contour of velocity.

I went tried already using the Matlab database but I don't get epected results. It is hard to interpret the code given in the database, do if anyone can help to relate the code with the velocity data I have would be a big help.

[Walter Roberson]

Velocity is a vector valued quantity, so it is not clear to me that plotting a contour makes sense. Consider that your x is an independent dimension and your y is an independent dimension, and your u and v are each dependent dimensions. That is four total dimensions, but a contour plot only makes sense for two independent dimensions and one dependent dimension. Unless, that is, you want to try the somewhat weird possibility of using contour3 by making one of the dependent dimensions into an independent dimension, such as

contour3(x, y, u, v)   %x, y, u are being treated as independent dimensions and v as dependent dimension

It seems to me that it would make more sense to use a quiver plot

[Mandar Kadwekar]

Thanks for your reply,

can I apply contourf if I have a a total velocity magnitude matrix dpendent on X&Y. I want to produce results similar to the picture I have attached.

[Star Strider]

Without the data themselves to work with, the only suggestion I have is to create a vector from ‘u’ and ‘v’ using the hypot function. It is relatively straightforward to interpolate ‘x’, ‘y’, and the resulting magnitude vector created by hypot to matrices to use with contourf.

Answer 1

[KSSV]

Let u,v be your velcity matrices.

w = sqrt(u.^2+v.^2) ;
figure(1)
pcolor(x,y,w) ;  % if throws error, transpose w 
colorbar
shading interp 
figure(2)
contourf(x,y,w)

[Mandar Kadwekar]

I am only using pcolor for my plot and not contour. I tried adding quiver command but I can only see pcolor result. I tried using hold on and hold off command to do this.

[KSSV]

It should show you arrow plots on pcolor. Attach your data and code.

[Mandar Kadwekar]

thanks for the help, I got the result now. I was just using wrong varaible.