MATLAB: Interpolate gridded matrix row-wise

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Hi, I have an 860 by 122 matrix producing a plot below.
I want to interpolate over NaN columns but not all the NaNs in the matrix. I tried using interp function but it gives strange value that are unreasonably wrong. See my code below and attached mat file
figure(1)
pcolor(Y1,Ydepth,sst_up_574); shading flat
set(gca,'Ydir','reverse')
set(gca,'xlim',[bin(1) bin(91)],...
          'ylim',[0 500],'fontsize',8,'xminortick','on','yminortick','on') 
       hold on
      hc = colorbar;
      rmap=jet(20);
      newmap=rmap(2:1:20,:);
      colormap(newmap);
      caxis([4 23]);
      grid on;
      box on
      set(gca,'Fontweight','bold','Fontsize',16);
      set(get(hc,'ylabel'),'string','Water Temperature (^oC)','rotation',270,'verticalalignment','bottom');
      ylabel('Depth (m)');
      xlabel('Date');
      title(['Water Temperature: Upstream SG574'], 'fontweight', 'bold','FontSize',18)

Best Answer

Normally you could achieve this easily by interpolating over rows with a function that does not extrapolate by default. I believe interp1 could do this (?). I used a slighly more messy approach, where I drew a polygon around the area of interest, filled all nans, then removed all points outside of the polygon.
Z = sst_up_574;
X = Y1;
Y = Ydepth;
%Scan rows and find first non-NaN
x = nan(size(X,1))
y = nan(size(Y,1))
for j = 1:size(Z,1)
    [~,c] = find(~isnan(Z(j,:))==true,1,'first');
    if ~isempty(c)
        x(j) = X(j,c);
        y(j) = Y(j,c);
    else
        x(j) = max(X(j,:));
        y(j) = max(Y(j,:));
    end
end
x(isnan(x))=[];
y(isnan(y))=[];
%Build a polygon
x = [x 0];
y = [y min(Y(:))]
%Find points inside of polygon
in = inpolygon(X(:),Y(:),x,y);
%Fill all NaNs
Zq = fillmissing(Z,'linear',2);
%Set values outside of polygon to NaN
Zq(~in) = NaN;
figure(1)
pcolor(X,Y,Zq); shading flat
set(gca,'Ydir','reverse')
set(gca,'xlim',[bin(1) bin(91)],...
    'ylim',[0 500],'fontsize',8,'xminortick','on','yminortick','on')
hold on
hc = colorbar;
rmap=jet(20);
newmap=rmap(2:1:20,:);
colormap(newmap);
caxis([4 23]);
grid on;
box on
set(gca,'Fontweight','bold','Fontsize',16);
set(get(hc,'ylabel'),'string','Water Temperature (^oC)','rotation',270,'verticalalignment','bottom');
ylabel('Depth (m)');
xlabel('Date');
title(['Water Temperature: Upstream SG574'], 'fontweight', 'bold','FontSize',18)
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