quiversc documentation

quiversc scales a dense grid of quiver arrows to comfortably fit in axes before plotting them.

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Contents

Syntax

quiversc(x,y,u,v)
quiversc(...,'density',DensityValue)
quiversc(...,scale)
quiversc(...,LineSpec)
quiversc(...,LineSpec,'filled')
quiversc(...,'Name',Value)
h = quiversc(...)

Description

quiversc(x,y,u,v) plots vectors as arrows at the coordinates specified in each corresponding pair of elements in x and y. The matrices x, y, u, and v must all be the same size and contain corresponding position and velocity components. By default, the arrows are scaled to just not overlap, but you can scale them to be longer or shorter if you want.

quiversc(...,'density',DensityFactor) specifies density of quiver arrows. The DensityFactor defines how many arrows are plotted. Default DensityFactor is 50, meaning hypot(Nrows,Ncols)=50, but if your plot is too crowded you may specify a lower DensityFactor (and/or adjust the markersize).

quiversc(...,scale) automatically scales the length of the arrows to fit within the grid and then stretches them by the factor scale. scale = 2 doubles their relative length, and scale = 0.5 halves the length. Use scale = 0 to plot the velocity vectors without automatic scaling. You can also tune the length of arrows after they have been drawn by choosing the Plot Edit tool, selecting the quiver object, opening the Property Editor, and adjusting the Length slider.

quiversc(...,LineSpec) specifies line style, marker symbol, and color using any valid LineSpec. quiversc draws the markers at the origin of the vectors.

quiversc(...,LineSpec,'filled') fills markers specified by LineSpec.

quiversc(...,'Name',Value) specifies property name and property value pairs for the quiver objects the function creates.

h = quiversc(...) returns the quiver object handle h.

The problem

Here's the problem: When you try to plot a dense grid of wind patterns using Matlab's built-in quiver function, things can get too crowded to make any sense out of what's going on:

load pacific_wind

figure
quiver(lon,lat,u10,v10)
axis tight % eliminates empty space
borders    % national borders for context

Example 1

Above, the 417x761 grid of wind vectors means there are more than 300,000 arrows in that plot. To put that into context, there are 761 arrows spanning the width of the plot, and that's probably about how many pixels the plot is occupying on your screen. In other words, if each arrow is about the size of a pixel, they're gonna be too small gain any understanding from.

So try the same thing, but this time with quiversc:

figure
quiversc(lon,lat,u10,v10)
axis tight
borders

Example 2: Define arrow properties

Make the arrows red and plot fewer of them by setting the density to 30 rather than the default 50:

figure
quiversc(lon,lat,u10,v10,'r','density',75)
axis tight
borders

Author Info

This function is part of the Climate Data Toolbox for Matlab. The function and supporting documentation were written by Chad A. Greene of the University of Texas at Austin.