Problem with polyfit function

Hi all,

I have 2 set of data, each of which is 31*12 (31 for number of days, and 12 for months)

Set1 = T3_All (%x-values)
Set2 = Tmax_All (%y values)

Since we don't have more than 28 or 29 days for some months, the data is filled with NAN.

when i use ployfit (code below), I am getting NaN for all values. I think that is because my arrays include NaN values.

How can I got the polyfit function to deal with the NAN values to give me the correct polyfit?

I couldn't upload any files as it seems there is a bug with the system !

Here is my code:

% Assigning arrays to data
T3_All=AllT3_Import;
Tmax_All=AllTmax_Import;

% Determining coefficients

coeff1 = polyfit(T3_All,Tmax_All,1); 

And the results I am getting:

coeff1 =
   NaN   NaN

Any help would be highly appreciated!

Answer 1

[Walter Roberson]

How can I got the polyfit function to deal with the NAN values to give me the correct polyfit?

You cannot. You need to be sure not to pass in data that contains nan.

mask = ~(isnan(T3_All) | isnan(Tmax_All));
coeff1 = polyfit(T3_All(mask), Tmax_All(mask), 1);

[D.J]

Brilliant ! Thanks a lot Walter !