# Plotting different color points based on array values

97 views (last 30 days)
Elena Zucchetti on 6 Mar 2023
Edited: Voss on 7 Mar 2023
I have an array and I want to plot it applying different colors depending on the values. If the value to be plotted is below a threshol the color is green, if above it should be red. All data should be connected by straight line.
Whit the code here I can only display values below the threshold.
How can I display all the values?
length1=length(DE);
for i=1:length(DE)
if DE(i)>=5
color='or';
else
color='og';
plot(data.Name_1(i),DE(i),color)
end
hold on
end

William Rose on 6 Mar 2023
One way:
x=1:100;
N=length(x);
DE=10*rand(1,N);
c=zeros(N,3); %allocate colors
for i=1:N, if DE(i)>5, c(i,:)=[1,0,0]; else c(i,:)=[0,1,0]; end, end
subplot(211); scatter(x,DE,50,c,'filled'); hold on
plot(x,DE,'-k'); hold off %add line connecting the points, as you requested
Another way:
clear
x=1:100;
DE=10*rand(size(x));
subplot(212); scatter(x(DE<5),DE(DE<5),'g','filled');
hold on
scatter(x(DE>=5),DE(DE>=5),'r','filled');
plot(x,DE,'-k'); %add straight lines between points
Try it. Good luck.

Les Beckham on 6 Mar 2023
Edited: Les Beckham on 6 Mar 2023
x = linspace(0, 10);
y = sin(x); % test data
yhi = y;
ylo = y;
threshold = 0.5;
idxlo = y <= threshold;
idxhi = y > threshold;
yhi(idxlo) = nan;
ylo(idxhi) = nan;
plot(x, yhi, 'ro-', x, ylo, 'go-')
grid on

Voss on 6 Mar 2023
Edited: Voss on 7 Mar 2023
data = struct('Name_1',randperm(50));
DE = 2.5+5*rand(1,50);
threshold = 5;
[~,idx] = sort(data.Name_1);
x = data.Name_1(idx);
y = DE(idx);
xy = [x(:) y(:)];
direction = diff(xy(:,2) > threshold);
do_interp_up = [direction == 1; false];
do_interp_down = [direction == -1; false];
do_interp = do_interp_up | do_interp_down;
N = size(xy,1);
new_xy = NaN(N+3*nnz(do_interp),2);
jj = 1;
for ii = 1:N
new_xy(jj,:) = xy(ii,:);
if do_interp(ii)
new_xy(jj+[1 3],1) = interp1(xy(ii+[0 1],2),xy(ii+[0 1],1),threshold);
new_xy(jj+2,2) = threshold;
if do_interp_up(ii)
new_xy(jj+[1 3],2) = threshold+[-1 1]*eps(threshold);
else
new_xy(jj+[1 3],2) = threshold+[1 -1]*eps(threshold);
end
jj = jj+3;
end
jj = jj+1;
end
low_idx = new_xy(:,2) <= threshold;
high_idx = new_xy(:,2) >= threshold;
hold on
plot(new_xy(low_idx,1),new_xy(low_idx,2),'g')
plot(new_xy(high_idx,1),new_xy(high_idx,2),'r')

### Categories

Find more on Multidimensional Arrays in Help Center and File Exchange

R2022b

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by