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Ancova analysis on two linear regressions (from microscopy data)

Posted 11 years ago
Hello everybody,

I would like to kindly ask for your help.
the results of the microscopy analysis I perform on a specific specimen are two images taken with different wavelengths (405 and 488).

It is possible to plot the intensities of a specific pixel at 405,x and 488,y (in a scatter plot for example) and to fit a linear regression line.
Changes in the regression slopes are observed depending on the treatments performed to the specimen, between condition A and B.
I would like to determine if two regressions are statiscally significant. I believe I need to perform an ANCOVA for that. However, I still wasn't able to compute it in mathematica specially because I have problems describing the nominal variable.

Could you please give me some tips?
Thank you very much for your time,
Ana

This is my procedure so far:
1.
Loading 4 images: A405, A488, B405, B488
2.
PixA405 = Flatten[ImageData[A405, "Bit16"]];
PixA488 = Flatten[ImageData[A488, "Bit16"]];
PixB405 = Flatten[ImageData[B405, "Bit16"]];
PixB488 = Flatten[ImageData[B488, "Bit16"]];
3.
TabA405A488 = Table[{PixA405[], PixA488[]}, {n, 1, PixNo}];
TabB405B488 = Table[{PixB405[], PixB488[]}, {n, 1, PixNo}];
4.
LinearFit1 = LinearModelFit[TabA405A488, {x}, x]
LinearFit2 = LinearModelFit[TabB405B488, {x}, x]
POSTED BY: Ana Gomes Barata
I am not super strong in statistic and I am not sure if I understood your problem correctly.
However you don't need LinearModelFit to fit a line between two points,

sA = (Flatten[ImageData[A488, "Bit16"]] - Flatten[ImageData[A405, "Bit16"]])/(488-405)
and

sB = (Flatten[ImageData[B488, "Bit16"]] - Flatten[ImageData[B405, "Bit16"]])/(488-405)
already contain all the slopes.



What kind of relation do you expect between sA and sB (namely the effect of the treatments)?
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