The data in the file do not appear to resemble the data in the image.
For those, the fillmissing function (R2016b and later releases) is likely the best option, however it will be necessary for you to experiment to get the desired result—
a = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1081705/Book2.xlsx', 'VariableNamingRule','preserve')
a(:,1:3) = fillmissing(a(:,1:3), 'makima', 'EndValues','extrap') % Experiment With The 'method' (Here: 'makima'), The 'EndValues' extrapolation use the same 'method'
x = a{:,1};
y = a{:,2};
z = a{:,3};
L = size(a,1);
xq = linspace(min(x), max(x), L);
yq = linspace(min(y), max(y), L);
[X,Y] = ndgrid(xq, yq);
Z = griddata(x, y, z, X, Y);
figure
surfc(X, Y, Z)
grid on
.
