# How to update main grid with a seperately created subgrid values

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Mustafa Alper Cetintas on 10 Aug 2021
Commented: darova on 12 Aug 2021
Hello dear all,
Currently, having a difficulty to design an algorithm to update a grid's Z values with another subgrid values.
The main grid is 93x315 X,Y and Z(with NaN values). X,Y horizontal coordinates and Z is elevation.
Have another (xq,yq and zq) grid which is 24x24, I call it subgrid. This subgrid has X,Y values which cover smaller area inside of the main grid but Z values are different as it was interpolated. How can I substitute main grid's Z values with subgrid's interpolated Z values by finding correct location using their X and Y values.
As this issue exceeds my abilities, I would be appreciated for any suggestions, Thank you, Alper.

darova on 11 Aug 2021
Here is an example
ind1 = X < min(x(:)) & X < max(x(:)); % indices inbetween smallest and largest 'x'
ind2 = Y < min(y(:)) & Y < max(y(:)); % indices inbetween smallest and largest 'y'
ind = ind1 & ind2; % here is a region inside big matrix
The question: is the region will have size 24x24?
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darova on 12 Aug 2021
happy to help

R2021a

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