using image command for data with three columns

I have a datset with three columns.

The first column contains the data of x axis points.

The second axis contains the data of y axis points.

The third column contains integer indices either 1,2,3 corresponding to each (x,y) point.

I want to color code the x-y axis according to the indices alloted to each pair (x,y) and Color array

Col = [1,1,0; 0.7,0.7,0.7; 0.929,0.694,0.125];

[Dyuman Joshi]

Do you want to plot a line plot or a scatter plot? Or something else?

[Sishu Shankar]

I want to plot a color coded plot, where I already have in the third column which colour to assign to each (x,y) point.

Say, the dataset looks like

dat = [ 0.3 0.4 1

0.5 0.8 2

0.1 0.1 3

0.5 0.4 2]

Col = [1,1,0; 0.7,0.7,0.7; 0.929,0.694,0.125];

for each (x_i,y_i), i have the color z_i = Col(i) associated but I am njot sure how to implement in MATLAB

[Dyuman Joshi]

I understood that.

But, how should the values be plotted - should it be a scatter plot or a line plot?

Answer 1

[Walter Roberson]

cmap = [1, 1, 0;
        0.7, 0.7, 0.7;
        0.929, 0.694, 0.125]

pointsize = [];
scatter(x, y, pointsize, third_column);
colormap(cmap);

[Sishu Shankar]

Thank you!

Answer 2

[Udit06]

Hi Sishu,

If you want a scatter plot, you can loop through each index and use the scatter function to plot all the points belonging to one index along with the color corresponding to the index in each iteration.

Here is the code implementation for the same:

% Replace these with your actual data
x = [1, 2, 3, 4]; % x data
y = [5, 6, 7, 8]; % y data
indices = [1, 2, 3, 1]; % indices data

% color array
Col = [1, 1, 0; 0.7, 0.7, 0.7; 0.929, 0.694, 0.125];

figure;
hold on; 

% Loop through each unique index to plot the points
for idx = 1:size(Col, 1)
    % Find the points that correspond to the current index
    current_points = (indices == idx);
    
    % Scatter the points using the corresponding row from Col
    scatter(x(current_points), y(current_points), [], Col(idx, :), 'filled');
end

xlabel('X axis');
ylabel('Y axis');
title('Color-coded x-y points by index');

hold off; 

[Sishu Shankar]

Hi Udit, Thank you!