How to Get a Genetic Map, Given the Physical Position and Genotype Data of Markers

Question

[Daniyal]

Hello, I am trying to estimate the genetic distances of my markers. I have physical positions (in Mb) and genotype data from a set of selected sample plants for each marker. Now, I want to perform QTL analysis using the R/qtl package, and as far as I know, it prefers genetic distances in centiMorgans (cM) rather than physical distances in base pairs.

How can I convert physical positions to genetic distances or construct a genetic map from this kind of data? Thank you!