I want to change the color of markers in scatter plot which are greater than the specified values but I am facing difficulty

I have the following code

But it keeps giving me the following weer

clc
clear
close all

d = 4;
N = 1000;
X = linspace(0,d,N);
func = @(X) 2*X.*cos(X.^2).*exp(sin(X.^2)) + 14;
limit = func(X);


x = 4*rand(1,N);
y = 25*rand(1,N);

figure(1),hold on
h = scatter(x,y,10,'markerfacecolor','b');
plot(X,limit,'k-','linew',1.3)

for i = 1:N
    
    if any(y(i) < limit)
        set(h,'YData','MarkerFaceColor','r','Markeredgecolor','r')    
    end
    
end

But it keeps giving me the following error

Error using matlab.graphics.chart.primitive.Scatter/set

Invalid parameter/value pair arguments.

Answer 1

[Walter Roberson]

        set(h,'YData','MarkerFaceColor','r','Markeredgecolor','r')    

It is possible to set YData of a scatter plot, and doing so successfully would change the Y coordinates of the markers. However, the new coordinates need to be the same kind of data as the original Y coordinates; double precision in your code. Instead, your code is trying to change the Y coordinates to instead be the character vector ['M' 'a' 'r' k' 'e' 'r' 'F' 'a' 'c' 'e' 'C' 'o' 'l' 'o' 'r']

I suspect you thought you were doing something like

  set(h,'YData', y(i), 'MarkerFaceColor','r','Markeredgecolor','r')    %NOT GOING TO WORK

with the intended meaning that you wanted to change the face color and edge color for the i'th point.

I would suggest

 mc = repmat([0 0 1], N, 1); 
 h = scatter(x, y, 10, mc, 'MarkerEdgeColor', 'flat');
 
 for i = 1:N  
    if y(i) < limit(x(i))
        h.CData(i,:) = [1 0 0];
    end 
end

But if I were doing it for myself, I would vectorize the calculation and build the mc color array once, like

mask = y < limit(x);
mc = repmat([0 0 1], N, 1); 
mc(mask,1) = 1; mc(mask,2) = 0; mc(mask,3) = 0;
h = scatter(x, y, 10, mc, 'MarkerEdgeColor', 'flat');

and that should build the plot the right way the first time, without needing to adjust the markers afterwards

Answer 2

[Star Strider]

See my Answer to your other Question.