Creating a scatter plot with three variables.

Hello, I am trying to create a scatter plot of some rain gauge data. I have three columns with data in them. My X variable is for Longitude, Y is Latitude and Z would be the rainfall totals. Each variable is a 31x1 double array. How can I get the Z variable to show up as individual points on the graph with color representing higher values?

Answer 1

[Star Strider]

This uses the value of ‘Z’ to scale the colors:

x = 1:20;
y = 1:20;
[X,Y] = ndgrid(x,y);                                        % Create Grids
Z = (X - 10).*(Y - 10);                                     % Create ‘Z’

figure
scatter3(X(:), Y(:), Z(:), [], Z(:), 'filled')              % Use ‘Z(:)’ To Scale Colors

Experiment to get the result you want with your data.

[Brandon Bush]

Thanks for the feedback. This made the plot, however I am not trying to make a 3d plot. It has to be a 2d plot with

 c = load('coast');
 hold on;
 u = load('us_state_map.mat');

as my grid.

[Star Strider]

Try this:

x = 1:20;
y = 1:20;
[X,Y] = ndgrid(x,y);                                        % Create Grids
Z = (X - 10).*(Y - 10);                                     % Create ‘Z’

figure
scatter(X(:), Y(:), [], Z(:), 'filled')

That should do what you want.

[Brandon Bush]

Thank you, this worked

[Star Strider]

My pleasure.

If my Answer helped solve your problem, please Accept it!

[María Verónica Alba Valencia]

Thak you, too.

[Star Strider]

My pleasure!

Answer 2

[Honglei Chen]

I would use scatterm, something like

scatterm(X,Y,5,Z)

The reference page can be found at

https://www.mathworks.com/help/map/ref/scatterm.html

HTH

[Brandon Bush]

Thank you for your answer, when I use this I get an error message that says "error using gcm: Not a map axes"

[Honglei Chen]

I thought you want to plot lat and lon on a map.