Read about interp2.
T = readtable('https://in.mathworks.com/matlabcentral/answers/uploaded_files/771628/excel%20table.xlsx') ;
T = table2array(T) ;
x = T(1,2:end);
y = T(2:end,1);
Z = T(2:end,2:end); % use fillmissing to fill NaNs
[X,Y] = meshgrid(x,y) ;
figure(1)
pcolor(X,Y,Z);
% do interpolation
m = 100;
xi = linspace(min(x),max(x),m) ;
yi = linspace(min(y),max(y),m);
[Xi,Yi] = meshgrid(xi,yi);
Zi = interp2(X,Y,Z,Xi,Yi);
pcolor(Xi,Yi,Zi)
