How to plot, in Matlab, a mollweide map projection given a lat vector (Nx1), a longitude vector(Mx1), and data points (NxM)

Question

I can do a simple pcolor or imagesc plot where

 dec=-90:1:90;
 ra=180:-1:-180;
 mydata=rand(181,361);
 imagesc(ra,dec,mydata)

how do I plot this with a mollweide projection using matlab?

I can do it in python quite easily, but the mapping functions in Matlab are not clear to me what I'm supposed to do.

My real data is not random, but the random data was easiest to generate here.

I always use [m_map](https://www.eoas.ubc.ca/~rich/map.html) for mapping. it is quite straightforward — shamalaia, Jul 20 '18 at 23:07
Everything is straightforward once you know how to do it. I am now reading up on m_map. — Tom Mozdzen, Jul 21 '18 at 23:40

score 0 · Accepted Answer · answered Jul 22 '18 at 17:56

OK, thanks to shamalaia for pointing me to m_map, which contains m_pcolor.

 figure(1);clf(1);
 dec=-90:1:90;
 ra=180:-1:-180;
 mydata=rand(181,361);
 m_proj('mollweide','clongitude',0);
 obj=m_pcolor(ra,dec,mydata); 
 shading interp; 
 m_grid('xaxislocation','middle','xtick',8,'ytick',7,'fontsize',7,'color','white');

 mymap=colormap('jet');
 colormap(mymap);
 h=colorbar('h');
 caxis([0 1]);

score 0 · Answer 2 · answered Jul 24 '18 at 23:09

Using Matlab's mapping commands - This does seem less intuitive than m_map.

Note: to use this code on the above example, set moonalbrefvec(1)=1;

I didn't like the labels produced, so I made my own.

clear;
figure(2); clf(2);
load moonalb % a 540x1080 matrix of values is loaded along with moonalbrefvec=[3;90;0]
moonalbrefvec(1)=3; % this is the subdivisions per degree - thus 180*3=540 & 3*360=1080
moonalbrefvec(2)=90; % NW lat value
moonalbrefvec(3)=180; % NW long value
mymap=colormap('jet'); mymap(1,1:3)=1;colormap(mymap);
axesm('MapProjection','mollweid','MapLatLimit',[-90 90],'Gcolor','white','GLineWidth',2.0,'MLineLocation',[-135 -90 -45 0 45 90 135],'PLineLocation',30) ; 
axis off;caxis([0 500]); 
grid on;
plabel('LabelFormat','none');
mlabel('on');
parallel='equator';
mlabel(parallel);
mlabel('FontColor','white');
mlabel('off');
gridm('on');
geoshow(moonalb, moonalbrefvec, 'DisplayType', 'texturemap');
plabel('off')
c=colorbar('location','southoutside','box','on','color',[0 0 0]);
c.Label.String='T_{sky} (K)';
c.Limits=[0 500];
c.Ticks=0:50:500;
c.FontSize=12;
textm(-5,-135,'3 h','color','white','fontsize',25);
textm(-5,-90,'6 h','color','white','fontsize',25);
textm(-5,-45,'9 h','color','white','fontsize',25);
textm(-5,0,'12 h','color','white','fontsize',25);
textm(-5,45,'15 h','color','white','fontsize',25);
textm(-5,90,'18 h','color','white','fontsize',25);
textm(-5,90,'18 h','color','white','fontsize',25);
textm(-5,135,'21 h','color','white','fontsize',25);

How to plot, in Matlab, a mollweide map projection given a lat vector (Nx1), a longitude vector(Mx1), and data points (NxM)

2 Answers2