Quiverc

Creates a color quiver plot with arrows colors according to the magnitude of the vector.

Description

This is a modified version of the function quiver [from C.M. Thompson] to plot velocity vectors as arrows with components (u,v) at the points (x,y) with the color corresponding to the magnitude of the vector and using the current colormap.

Tip: for best results, add set(gcf, 'InvertHardCopy', 'off') after the function to keep the black background on the hardcopy. See attached examples.

• Acknowledgements: This submission has inspired the following:; quiverc2, quiverc2wcmap
• MATLAB release: MATLAB 5.3 (R11)

[Klaas Hartmann]

I find the output of quiverc easier to interpret than that of quiver. My only qualm is that it runs a bit slow with the data I am plotting -- I wan't to show a sequence of quiver plots. Also it doesn't seem to handle NaNs in the data automatically (just replace them with 0s)

[Peter Slovinsky]

I was working with quiver plots to show current velocity and direction from a moving vessel. The quiverc is perfect for creating a figure that is easy to qualitativy interpret.

[Kwijibo Lefever]

Not as fast as quiver for large vector/velocity field. But fine otherwise.

[Colin Ned]

great job, save me much time to write code

[Gavita Regunath]

Brilliant and extremely useful! Thanks!

[tuna kaskati]

 

[Ching-Fang Lee]

It's a very useful tool for ploting! Thanks!

[David Kolin]

Excellent, except that the color mapping is incorrect if the current colormap is longer than 64. Changing the two int8 calls in quiverc to int16 fixes this problem.

[Alison Rogers]

Thanks! This is very useful.

[Burak eral]

Hi Bertrand;

I am using your cool code quiverc for plotting velocity fields that evolve over time… In your code you normalize colormaps so that red in colorbar refers to max velocity with in frame… I am trying have a global colormap where I insert max value velocity value within my frames so red refers to this value at all times…

I tried to change max(vr(:)) in code below with my global max value but it does not work…

vr=sqrt(u.^2+v.^2);
vrn=round(vr/max(vr(:))*64);
CC=colormap;
ax = newplot;
next = lower(get(ax,'NextPlot'));
hold_state = ishold;

Do you have an idea how I can go around this ?

Thanks in advance
Burak

[Vinesh Rajpaul]

Great file, thanks! But -- is there any way to use quiverc.m to create a colour quiver plot, but with all arrows plotted with same lengths? I.e. magnitude of vectors to be indicated solely by color and not length. It's redundant to indicate magnitude both by length and color; moreover, some vectors are often so small (relative to others in the field) that they are "invisible", in which case the colormap is useless anyway. Thanks.

[JH]

good job, but one comment: when I use h=quiverc(x,y,U,V,S), it seems the code can not return h? In other words, quiverc(x,y,U,V,S) works, but h=quiverc(x,y,U,V,S) does not work.

[Tiago Leal]

??? Attempted to access CC(5,1); index out of bounds because size(CC)=[2,3].

Error in ==> quiverc at 134
    c1= CC(ii,1); c2= CC(ii,2); c3= CC(ii,3);

I have this error when I run the codes. C(x,1) x is alwyas different and bigger than 2. Anyone can help me??

[Tiago Leal]

I already found the problem. My code had colormap(gray(2)) before the plot.