imagesc 将 NaN 值显示为非 NaN

Question

下图中的红色补丁显示了数值模型的域。绿色补丁显示地球。

我想为模型域中的点创建一个矩阵，其中包含地球表面以上的高度值。

我使用以下代码：

close all
clear all

%%%slope coefficient
a=1/50;

%%%resolution
dx = 500;
dz = 2.5;

%%%define domain
xi = 0:dx:200e3;
zi = 0:dz:6e2;
m=length(zi);%domain dimension
n=length(xi);%domain dimension

%%%max z where the slope starts
zs = find(zi==max(zi)); 


for ii=1:n %for every x

    zslope = -a*xi(ii)+zi(zs);%equation of the slope

    zz(ii)=zslope;
   if zslope>=0 %if the slope is still in the domain (z>0)
     for jj=1:m %for every z

       if zi(jj)>=zslope %above the slope

         Z(jj,ii) = zi(jj)-zslope; %height above the slope

       elseif zi(jj)<zslope %below the slope (ground)

         Z(jj,ii)=NaN; 

       end
     end%for on z

   elseif zslope<0 %the slope is no longer in the domain

       for jj=1:m %for every z

          Z(jj,ii) = zi(jj)-zslope; %height above the slope

       end
   end
end%for on x

这似乎工作正常：

figure;
imagesc(Z)
colorbar

事实上，点 240 的值正如人们所期望的那样是 600。

问题

问题是在工作区中 Z 矩阵充满了 NaNs！

当值是 NaN 时，imagesc 如何不显示 NaN 值？

注意

如果我评论这些行

elseif zi(jj)<zslope %below the slope (ground)

     Z(jj,ii)=NaN;

没问题。

Answer 1

NaN 显示为颜色条中的最低值（反之亦然）。如果要从图中删除 NaN 值，可以使用 isnan 和 AlphaData 属性.

imagesc(Z,'AlphaData',~isnan(Z))

imagesc 将 NaN 值显示为非 NaN

imagesc showing NaN values as not NaN

matlab

nan