How to use least square fit to 2D matrix data

I have a set of OLR data in longitude x time, giving a size of 180 x 31, being xaxis the longitude and y-axis lag time in days. How would you measure the phase propagation of the minimum values (in contour), starting at the minimum on day 0?

I know it has to do with a least square fit, but I dont know how to do it

Answer 1

[Matt J]

[~,location]=min(Data);

[Luis Jesús Olvera Lazcano]

I understand, but how can I plot the whole least square method result. I mean, the line which I can measure the slope = phase propagation

[Matt J]

If you mean you want to do a line fit to the minima locations, then,

[~,location]=min(Data);

p=polyfit(0:30,location,1);

slope=p(1);

[Luis Jesús Olvera Lazcano]

Ohhh, but how do i put it in the same pcolor graph?

Im sorry Im a little lost with this, but thanks youre helping me a lot