scatterplot shows RowIDs as points and points as a color map

Hi,

I would like to plot a scatter plot but I would like to show the points in the scatterplot by point IDs. For example, if I have RowIDs from 1 to 10, I have two columns X and Y. I want to show a scatter plot of X and Y but the points should show the point IDs (1-10). Also, I would like to include a colormap so that these points have a color spectrum.

Can anybody suggest me a method how to implement in MATLAB? (Please see the image of what I want to do)

Thanks in advance.

Answer 1

[arich82]

Would something like this work?

n = 30; % number of data points
cmap = jet(n); % builtin colormap; could choose another...
C = mat2cell(cmap, ones(1, size(cmap, 1)), 3); % reshape for 'set'

% dummy data
k = [1:n].';
t = (k - 1)/n;
r = (t - 1).*cos(2*pi*2*sqrt(t));
%
x = 10*((1 + r)/2);
y = x;
z = t;
%figure('WindowStyle', 'docked');
%surf([x, x], [y, y], [z - eps, z + eps], 'EdgeColor', 'interp');

% plot numerical data
hf = figure('WindowStyle', 'docked');
ha = axes;
axis(ha, [0, 10, 0, 10]);
ht = text(x, y, num2str(k));
set(ht, {'Color'}, C)
set(ht, 'FontWeight', 'bold');
colormap(cmap);
colorbar;

Note: using the 'set' command with cell arrays can be a little cumbersome (in my opinion), as there seem to be a number of gotchas; you could just as easily loop through ht:

for ind = 1:n
  set(ht(ind), 'Color', cmap(ind, :));
end

Let me know if this works for you.

--Andy

[Damith]

Andy.

I am planning to use scatterplot function available in matlab. Is there a way I can include this with scatterplot function?

If I use scatter function what should be my X and Y data in your code.

[arich82]

I assume by "scatterplot", you mean "scatter" (otherwise, I'm not familiar with that function).

Not to be glib, but is there a good reason why you want to use the "scatter" function instead of "text"? As far as I know, the only marker types available in "scatter" are a limited set of symbols (non-alpha numeric); cf. scatter, "markertype — Marker type".

The calling for "scatter" and "text" are quite similar; you'd use the same x-y data as before. To plot the same data using scatter and square markers, you'd use, e.g.:

marker_size = 25;
marker_type = 's'
hs = scatter(x, y, marker_size, cmap, marker_type);

Note that marker_size and marker_type could instead be vectors of length(x) to assign different properties to each data point, but as mentioned, arabic numerals are not one of the valid marker types for scatter.

Let me know if there's a good reason to not use "scatter". From my perspective, "text" seems to meet your stated requirements. If it doesn't, please explain why.

--Andy

[arich82]

Damith--

Not sure if you're still interested in this, but I now see that "scatterplot" is in a toolbox I don't have. From this answer, you can get the x-y data from from "scatterplot" by getting the plot handle from the children:

hf = scatterplot(rand(20,2)); % figure handle
ha = get(hf,'Children'); % axis handle
hp = get(ha,'Children'); % plot handle
X = get(hp,'XData');
Y = get(hp,'YData');

You should then be able to use the "text" code described above to produce the desired plot.

[Damith]

Hi,

Thanks all for your comments. I made this to work. Please look at the following code. But I need to show the points (as numbers) in black color. But it is showing in different colors according to the colormap. How can I make it show all the points (as numbers) in black color.

Thanks in advance.

n = 6; % number of data points
cmap = jet(n); % builtin colormap; could choose another...
C = mat2cell(cmap, ones(1, size(cmap, 1)), 3); % reshape for 'set'
k = [1:n].';
marker_size = 25;
marker_type = 's'
xlim([2 6]),ylim([2 6])  
ht = text(Ob_All_avg, WGEN_All_avg, num2str(k));
set(ht, {'Color'}, C)
set(ht, 'FontWeight', 'bold','FontSize',18,'edgecolor','none');
colormap(cmap);

       box on
       line([2,6],[2,6],...
            'linewidth',0.6,...
            'color',[1,0,0],'LineStyle','--');
       set(gca,...
            'xlim',[2,6],...
            'ylim',[2,6]);
       axis square;
       xlabel('TRMM (1998-2012)','FontSize',14)
       ylabel('WGEN generated 10000 yrs','FontSize',14)
       title('Daily Mean','FontSize',14)

[arich82]

I'm confused: I though you said "I would like to include a colormap so that these points have a color spectrum". Do you no longer want this? If not, simply omit the building and use of C.

It appears,

set(ht, {'Color'}, C)

is how you're changing the text color. Try omitting that line (place a % in front), or try

set(ht, 'Color', 'k'); % equvivalent to set(ht, 'Color', [0, 0, 0]);

to change all the text to black.

I hope this helps; please clarify what you're expecting if it doesn't.