pcolor and plot graphs transparent

[Sophia Lianou]

Dear Sir/Madam,

I wonder if you can help me with my code, or to find the appropriate help to resolve my issue. 

I would like to make a color-map, using pcolor, to be plotted on top of another graph, but without the color-map covering the first graph. I can not make the color-map to be "transparent" on top of the first graph. 

I am new in octave, and the plotting is done using gnuplot. Thanks in advance. I append the code I use below.

Kind regards

Sophia 

data1 = load ('eso540_030.pht'); % 

x1 = data1(:,1); 
y1 = data1(:,2); 
mvo1 = data1(:,10); 
mio1 = data1(:,19); 
col1 = mvo1 - mio1; 
% 
dcol=0.1; 
colbin = 0.3:dcol:1.2; % binning in color 
di = 0.1; 
ibin = 23.6:di:27.6; % binning in magnitude 
% 
density = zeros(length(colbin),length(ibin)); % stellar density 
% 
for i = 1:length (colbin); 
    for j = 1:length (ibin); 
        density(i,j) = length(mio1(col1>colbin(i)-dcol/2 & col1<=colbin(i)+dcol/2 & mio1>ibin(j)-di/2 & mio1<=ibin(j)+di/2)) ; 
    end 
end 
% 
[xx yy]=meshgrid (colbin,ibin); 
%   
 figure(2); clf 
 plot(col1,mio1, '+', 'Color', [0.65 0.65 0.65], 'MarkerSize',2); 
 % 
 hold on 
 pcolor(xx, yy, density'); % this over-plots and hides some points - can it be transparent? 
 shading interp; 
 colormap (flipud(hot)) 
 % 
 axis([-0.4 2.2 22.2 28.2]) 
 axis square