Error in blmod_exp_startpars() when end of AIF contains zero values

[pontusps]

Hi,

Love the package, keep up the good work!

I was playing around with fitting input functions, and I think I found a potential issue in blmod_exp_startpars(). When I have noisy data and get some negative values at the end of my AIF I would like to set them to zero. However, doing so means that line 20 bugs out, were it tries to do some fitting of the end of the AIF:

  exp3_mod <- lm(log(abs(activity)) ~ time, data = blood_exp_part3)

Produces

Error in lm.fit(x, y, offset = offset, singular.ok = singular.ok, ...) :
NA/NaN/Inf in 'y'

I assume this is due to log(abs(0))producing -Inf. Perhaps any zero values inside blood_exp_part3 can be filtered out?

Here's a reproducible example (I think):

blooddata <- create_blooddata_bids(kinfitr::pbr28$jsondata[[1]])
blooddata <- bd_blood_dispcor(blooddata)
aif <- bd_getdata(blooddata, output = "AIF")
aif$aif[length(aif$aif)] <- 0

blood_fit <- blmod_exp(aif$time,
                       aif$aif,
                       Method = aif$Method, multstart_iter = 1)

[pontusps]

Actually, I see now that the user don't even have to set negative values to zero themselves. The fun blmod_tidyinput called early in blmod_exp sets all negative values in the AIF to zero with line

blood$activity <- ifelse(blood$activity < 0, yes = 0, no = blood$activity)

meaning that if you have a single negative value at the end of the AIF, then blmod_exp_startpars will always error out at line 20.

[mathesong]

This is adddressed in PR #12 and fixed. Thanks so much for the contribution!