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  1. Hi all, I have edited twilight events from Migrate Tech tags using preprocessLight in TwGeos. I have then converted to TAGS format using the function BAStag2TAGS. I have been able to follow the workflow for GeoLight up until the function mergeSites, after this step I get the following error: "Error in solve.default(fit$hessian) : Lapack routine dgesv: system is exactly singular: U[1,1] = 0." ​My code up until this point looks like this: # so we have to extract twilights tw<-TAGS.twilights[TAGS.twilights$twilight>0 & TAGS.twilights$excluded==0 & TAGS.twilights$datetime<as.POSIXct("2017-06-12", tz="UTC"),] # make pairs tw$datetime[tw$twilight==2]<-tw$datetime[tw$twilight==2] gl_twl<-data.frame(tFirst=tw$datetime[which(diff(tw$datetime)<20)], tSecond=tw$datetime[which(diff(tw$datetime)<20)+1], type=tw$twilight[which(diff(tw$datetime)<20)]) TAGS.twilights$datetime<-as.POSIXct(TAGS.twilights$datetime, tz="UTC", format="%Y-%m-%dT%T") cL <- changeLight(gl_twl, quantile = 0.95, days = 5) mS <- mergeSites(gl_twl, site = cL$site, degElevation = elev, distThreshold = 400) ​If anyone has encountered this error before and can shed light on what I am doing wrong, it would be much appreciated. ​Thanks, Leah