Plot RGB triplets from a matrix as markers 'o'

I have a matrix B 6-by-3. I want using a for loop to plot six different coloured markers 'o' in the same figure and in one line (y=0).

Each row has 3 elements of 0 and 1 representing RGB triplet colors.

My code is:

% Define axis limits

x = linspace(0,10,10);
y = linspace(0,10,10);
xlabel('X-axis');
ylabel('Y-axis');
axis([0 10 0 10]);
B =[1     0     0  
    0     1     0   
    1     0     1  
    0     1     1   
    0     0     1   
    0     0     1];
for k=1:6
    VW = B(k,:);
    plot((VW),'o','LineWidth',5);
    hold on
end
hold off

I get the following figure with wrong colors

Any help is appreciated.

Thanks a lot.

Stelios Kas.

Answer 1

[Cris LaPierre]

Your plot command is adding 3 points each time. Try this. It specifies a unique x location for each row of C, and colors the marker using the RGB combo for that row. Y=0 for all 6 points.

Note that the order of your commands matters when formatting the appearance of the figure, since calling plot with the syntax you use creates a new axis.

% Define axis limits
C =[1     0     0  
    0     1     0   
    1     0     1  
    0     1     1   
    0     0     1   
    0     0     1];

scatter(1:size(C,1),0,[],C,'filled');
xlabel('X-axis');
ylabel('Y-axis');
axis([0 10 0 10]);

[Stylianos]

Dear Chris, this is what I want but when I run your code I get the followig error message:

Error using scatter (line 107)

X and Y must be vectors of the same length.

Error in TestColor (line 9)

scatter(1:size(C,1),0,[],C,'filled');

Thank you very much.

Stelios Kas

[Cris LaPierre]

Ah, you are probably using a slighly older version of MATLAB. Here's updated code.

% Define axis limits
C =[1     0     0  
    0     1     0   
    1     0     1  
    0     1     1   
    0     0     1   
    0     0     1];

scatter(1:size(C,1),zeros(1,size(C,1)),[],C,'filled');
xlabel('X-axis');
ylabel('Y-axis');
axis([0 10 0 10]);

[Stylianos]

Thank you very much Chris.

Now it works, I use Matlab 2019b.

Much obliged.

Stelios Kas

Answer 2

[Fangjun Jiang]

Use 'color' to specify color in plot()

x = linspace(0,10,10);
y = linspace(0,10,10);
xlabel('X-axis');
ylabel('Y-axis');
axis([0 10 0 10]);
B =[1     0     0  
    0     1     0   
    1     0     1  
    0     1     1   
    0     0     1   
    0     0     1];
for k=1:6
    VW = B(k,:);
    plot((VW),'o','LineWidth',5,'color',VW);
    hold on
end
hold off

[Cris LaPierre]

This code is likely not doing what you think. Plot a single row to confirm.

x = linspace(0,10,10);
y = linspace(0,10,10);
xlabel('X-axis');
ylabel('Y-axis');
axis([0 10 0 10]);
B =[1     0     0  
    0     1     0   
    1     0     1  
    0     1     1   
    0     0     1   
    0     0     1];
for k=1
    VW = B(k,:);
    plot((VW),'o','LineWidth',5,'color',VW);
    hold on
end
hold off

●

[Fangjun Jiang]

Yes. I only provided answer regarding 'color'. Didn't pay attention to what needs to be plotted. Can still use plot() to do it.

axis([0 10 0 10]);
B =[1     0     0  
    0     1     0   
    1     0     1  
    0     1     1   
    0     0     1   
    0     0     1];
for k=1:6
    VW = B(k,:);
    plot(k,0,'o','LineWidth',5,'color',VW);
    hold on
end

●

[Stylianos]

Dear Jiang.

The code works fine.

Thank you very much.

Much obliged.

Stelios Kas