Small molecule - calibration curve error: Matrix must be positive definite MartijnvF  2020-03-26

Dear all,

I am trying to use Skyline to see if it will be suitable in our clinical laboratory for quantification and monitoring of MS performance. I am getting an error I cannot find anything previous help on. The calibration curves are not showing:

Error: Matrix must be positive definite.

Cheers for any help, much appreciated.


Nick Shulman responded:  2020-03-26

The error is happening because the regression weight (at "Settings > Molecule Settings > Quantification") is "1/x" and two of your replicates have the "Sample Type" set to "Standard" and their Analyte Concentration is 0.

You should change the Sample Type of those replicates to "Blank" so that Skyline does not try to include them in the linear regression to determine the slope of the calibration curve.

-- Nick
MartijnvF responded:  2020-03-26
Ah of course. Thanks for the quick reply!