output of interp2 is single - why?

when I use the following code, the output zcovis is a single rather than a double.

if true
  surf(xb,yb,zb)
  [xcovis,ycovis]=ginput(1);
  zcovis = interp2(xb,yb,zb,xcovis,ycovis);
end

xb,yb,zb are imported data but xb,yb should be consistent with meshgrid format (zb is height above surface not a third coordinate)

why is zcovis a single? I'd like to use it to place a text comment on a another figure:

if true
  text(0.1,zcovis+4.2,'COVIS')
end

[KSSV]

Check the classes of xb,yb and zb..they could be single.

[Walter Roberson]

What are class(xb), class(yb), class(zb) ?

Answer 1

[ANKUR KUMAR]

It's because of your xb,yb,zb, xcovis and ycovis are single. If you want your output in double, just use double before using interp2.

zcovis = double( interp2(xb,yb,zb,xcovis,ycovis));

[Karen Bemis]

thanks, this and the previous comment clarify what I hadn't noticed before:

 while xb and yb are doubles, zb is actually single.

[Walter Roberson]

zcovis = interp2(xb, yb, double(zb), xcovis, ycovis);

[ANKUR KUMAR]

Make all inputs having the same class. This works well, as suggested by Walter Roberson.