# How to retrieve z value from surf plot given x and y?

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Kyle Gao on 19 Sep 2018
Commented: Kyle Gao on 19 Sep 2018
I got a surface useing:
s= surf(X, Y, Z)
Since the X, Y, and Z are discrete, I want to get the consecutive value of Z. For example, the origin data X and Y are all integers, and I don't the relationship between XY and Z, I want to get the z value where X = 1.87 and Y = 2.9. Is it possible? What should I do?

Cedric Wannaz on 19 Sep 2018
Edited: Cedric Wannaz on 19 Sep 2018
where Xq and Yq are defined using the values given in your question.

Kyle Gao on 19 Sep 2018
Thank you so much for your help! But I still need the query grid with a certain spacing value by using interp2. My problem is that I can't have the spacing value (or the grid), it needs to give me the Z value for a random X and Y. Any ideas?
Cedric Wannaz on 19 Sep 2018
Unless I misunderstand your question, you can just set
Xq = 1.87 ;
Yq = 2.9 ;
and have Zq with
Zq = interp2( X, Y, Z, Xq, Yq ) ;
Kyle Gao on 19 Sep 2018
Yeah! This solved my question perfectly!

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