Using two colormaps on the same image (no subplots)

Hi there, I have this code as shown below and I am trying to plot a colormap for topography first and then plot some data as a scatter graph on top where the colours of data points represent a date.

I am trying to define both colormaps so that matlab keeps them seperate but it keeps plotting them bpth on the same colorescale (please see my code).

load('x_data.mat')
load('y_data.mat')
load('z_data.mat')
% set axis 
h=[30.3 30.45 40.7 40.8];
lat_lon_proportions(h) %function taken from Jonathen Sullivan - available from https://uk.mathworks.com/matlabcentral/fileexchange/32462-correctly-proportion-a-lat-lon-plot
pcolor(X,Y,Z); %shades topography 
shading interp
m.EdgeColor = 'none'; % hides edges so looks pretty 
% map personalising
xlabel('Longitude (deg, E)');
ylabel('Latitude (deg, N)')
hold on 
topo=demcmap([min(Z(:)) 800], 40 ) % defined elevation limits 
cb=colorbar; % inserts colorbar 
set(get(cb,'label'),'string','Elevation (km)');
%set axis limits 
xlim([30.3 30.45])
ylim([40.7 40.8])
hold on 
%read in dates 
DateString = {'2012/06/11';	'2012/06/11';	'2012/06/12';	'2012/06/12';	'2012/06/12';	'2012/06/12';	'2012/06/12';	'2012/06/14';	'2012/06/15';	'2012/06/22';	'2012/07/07';	'2012/07/07';	'2012/07/07';	'2012/12/14';	'2013/04/23'};
formatIn = 'yyyy/mm/dd';
dates= datenum(DateString,formatIn);
% read in locations (initial velocity model) 
Lat=[40.760973	40.757441	40.759563	40.758157	40.760622	40.754624	40.761657	40.757445	40.760271	40.759577	40.760978	40.762381	40.760268	40.757441	40.751802];
Long=[30.406552	30.390829	30.402853	30.404705	30.40794	30.387133	30.38527	30.394529	30.409328	30.421357	30.413954	30.4084	30.405627	30.390829	30.379737];

%% Plot 2D 
y2= Lat;
x2= Long; 
d= dates;
sz=70;
hold on 
scatter(x2,y2,sz,d,'filled')
xlabel('Longitude')
ylabel('Latitude')
set(gca,'color',[64 64 64]/255,'FontSize',18)
dpoints=colormap(autumn);  % shows it from red to yellow 
c=colorbar('southoutside');
c.Ticks=[735040 735190 735330]
c.TickLabels={'June 2012','November 2012','April 2013'}
% define color maps 
cmap = [topo;dpoints];
colormap(cmap);

Any help would be fantastic

Many thanks in advance

[Adam]

If you don't need to visualise the colourmap itself for the scattered points you can always map the points mathematically onto your colourmap so you end up with a matrix of true RGB colours to pass to the scatter function as colours. This matrix would be of 1st dimension equal to the number of x and y points and 2nd dimension 3 (RGB).

Otherwise you will have to do the multiple overlaid axes solution pointed to by KSSVs answer, but beware that managing two axes whose positions are supposed to totally overlap can cause problems (e.g. what someone showed in a reply to that answer - once you start having x labels and things like that the positions of the two axes are generally not coincident and it is difficult to make them so)

[P_L]

Hi Adam, Thank you for getting back to me. I have taken your advice and taken to specifying the colours for a subset of data points as show below :

My question now is that how would I get my colorbar to work? because right now it just shows the same colours as the one for the elevation

Many Thanks

L1 = (d >= 735030 ) & (d <= 735050);  % Logical Subscripts For Condittion #1
L2 = (d >= 735051 ) & (d <= 735210);
L3 = (d >= 735211 ) & (d <= 735220);
L4 = (d >= 735221 );

scatter(x2(L1),y2(L1),sz,d(L1),'b','filled');hold on
scatter(x2(L2),y2(L2),sz,d(L2),'r','filled');hold on 
scatter(x2(L3),y2(L3),sz,d(L3),'g','filled');hold on 
scatter(x2(L4),y2(L4),sz,d(L4),'y','filled');
xlabel('Longitude')
ylabel('Latitude')
set(gca,'color',[64 64 64]/255,'FontSize',18)

c=colorbar('southoutside');
c.Ticks=[735040 735190 735330]
c.TickLabels={'June 2012','November 2012','April 2013'}

[Adam]

You can only have one colourbar per axes (corresponding to the one colourmap per axes) so as mentioned above, mapping to rgb values for your scatter plot works so long as you don't want to see a colourbar for them (you can create your own colourbar, but that is a lot of effort!)

Answer 1

[KSSV]

Refer here: https://in.mathworks.com/matlabcentral/answers/194554-how-can-i-use-and-display-two-different-colormaps-on-the-same-figure