How do i omit NaN values from polyfit?

I am pulling data from an excel sheet that has empty cells in it which appear as NaNs. I am plotting the data in this excel file, and i want a best fit line to go through it. If i try to use the polyfit function, it returns NaN values because of the empty cells in the excel sheet. Is there anyway i can have the sheet omit the NaN values and only look at the cells with data in them?

   filename = 'NB-Aroostook.xls';

   numData = xlsread(filename);

   [rows, columns] = size(numData);

    x=(1:rows);

    length= x.';

    maxt=numData(1:rows,3);

   figure(1)

   hold on;

    plot(length, maxt, 'LineWidth', .2);

    pbaspect([3 1 1]);

    fit1=polyfit(length,maxt,1);

    plot(length,fit1,'Color','k');

    xlabel('Year');

    ylabel('Maximum Monthly Temperature (°C)');

Any help is appreciated!

Answer 1

[Akira Agata]

How about the following?

filename = 'NB-Aroostook.xls';
numData = xlsread(filename);
maxt = numData(:,3);
length = (1:size(numData,1))';
idx = any(isnan(maxt));
fit1 = polyfit(length(~idx),maxt(~idx),1);

[car]

works like a charm! thanks!

[Akira Agata]

+Small improvement:

Looking at my script again, I found any function in the 5th line is unnecessary. Please revise the line as follows.

idx = isnan(maxt);