find the mean of values which are inside the inpolygon

hi i have written a code for satellite data- file format HDF5. i have chosen a latitude longitude. also i plotted a map as i wanted (attached), but i don't know how to get mean of those values(red dots) which are inside the inpolygon. kindly see the fig so u can get idea about what i want.

Answer 1

[Chad Greene]

The inpolygon function makes this pretty easy. It tells you the indices of all points inside a given polygon. Here's an example:

% Define and plot some scattered data points: 
lon = 100*rand(800,1); 
lat = 100*rand(800,1)-60; 
z = 10*sind(lat)+5*cosd(lon)+rand(800,1); 
plot(lon,lat,'.','color',[.08 .69 .1])

% Define and plot a box of interest: 
boxlat = [-5 -20 -20 -5]; 
boxlon = [48 48 62 62]; 
hold on
plot(boxlon,boxlat,'r-')

% Find indices of all data points inside the box: 
ind = inpolygon(lon,lat,boxlon,boxlat); 

% Plot the data points inside the box: 
plot(lon(ind),lat(ind),'ko')

% Calculate mean of all data points inside box: 
zbar = mean(z(ind))