get the linear fitting for all the possible X and Y combination

Question

Kunli Dong 2014-7-27

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回答： Image Analyst 2014-7-27

Hi,

I have the X data [30 60 80 100]

for the first X value (the 30) it could corresponds to four Y values 0.1 0.2 0.3 0.4

for the second X value (the 60) it also corresponds to four Y values 0.5 1.0 1.5 2.0

for the third X value (the 80) it also corresponds to four Y values 1.5 2.0 2.5 3.0

for the fourth X value (the 100) it also corresponds to four Y values 2.5 3.0 3.5 4.0

That is to say, I have 4*4*4*4=256 possible combinations of (X,Y), and thus 256 possible slopes.

So far, I only know that the linear fitting can be obtained by using the code: polyfit(x,y,1) Can anyone please tell me how to get all the 256 possible slopes?

thanks

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Answer 1

Image Analyst 2014-7-27

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在 MATLAB Online 中打开

Not sure how you get 256. You have 4 X, and for each X you have only 4 Y, so that's 16 slopes. The first X only uses those Y and not any of the other Y is what you said. Similar for the other X - they use only 4 particular Y, not all the Ys.

How about this:

X = [30 60 80 100]
Y = [...
  0.1 0.2 0.3 0.4;
  0.5 1.0 1.5 2.0;
  1.5 2.0 2.5 3.0
  2.5 3.0 3.5 4.0]
for col = 1 : length(X)
  for row = 1 : size(Y, 1)
    slope(row, col) = Y(row, col) / X(col);
  end
end
% Print 16 slopes to command window:
slope