# How to Fit Tabular Data

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Christopher Dottellis on 19 Jan 2021
Answered: Nitin Kapgate on 9 Feb 2021
I have a table with two variables, x and y. For each x,y pair there is a z.
I'm trying to find a two variable function that can represent this table. I have been trying to use fit() but it says that the format of my vectors is off. So I did the example and looked at the three vectors loaded in.
load franke;
surffit = fit([x,y],z,'poly23','normalize','on')
I find that the vectors , x, y, and z are all the same dimension. However, in my mind z = f(x,y) should be a matrix of values with dimensions size(x) by size(y). What is this fit function actually fitting then?
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Christopher Dottellis on 19 Jan 2021
To clarify, this data is sparse. Might it just be easier to create the function by hand?

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### Answers (1)

Nitin Kapgate on 9 Feb 2021
'z' vector should be of the same size as 'x' and 'y' vectors. The fit function tries to approximately fit a curve or surface to the data using different fitting techniques (fit type) etc.
You can refer to this example that demonstrates how to fit a surface using variables in a MATLAB Table.
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