Is original wolfAlps module unstable with changed parameter (MeanPixelQuality)?

[C M]

Hi everyone,

I am still trying to get rid of various errors in my adaption of wolfAlps. Now I have one that also seems to appear in the original wolfAlps module if MeanPixelQuality
is higher. I tried

MeanPixelQuality = 0.94 instead of 0.84.

This leads to the error

 "'vec' must be sorted non-decreasingly and not contain NAs"

I am pretty sure that things break down in line 635 / 636 of the original wolfAlps.R. 

# Now each wolf has its subset of cells as potential next locations for dispersal
    # Probability of going to the potential next locations regarding their directions
    headDispersers <- of(agents = dispersers, var = "heading")
    nextLocs[,nextAngle:={
      dnorm(mean = 0, sd = params(sim)$wolfAlps$sigma, # calculate the probability using the Normal distribution of ...
            subHeadings(angle1 = headDispersers[id], # ... the rotation of each wolf's heading to ...
                        angle2 = towards(agents = turtle(sim$wolves, who = whoDispersers[id]), # ... the direction towards each of its next potential locations
                                         agents2 = cbind(x = x, y = y))
            )
      )}, by = id] # data.table use of by = id, so each of the above happens within each id


    # Probability of going to the potential next locations regarding habitat suitability
    data.table::set(nextLocs,,"suitabilityValGood", sim$suitabilityValGood[nextLocs$indices])


    # Probability of going to the potential next locations regarding the directions, habitat suitability and other wolves presence
    data.table::set(nextLocs,,"prob", nextLocs$nextAngle * nextLocs$suitabilityValGood * nextLocs$empty)
    probLoc <- runif(n = NLcount(dispersers), min = 0, max = 1)
    setkeyv(nextLocs, c("id"))
    # Selected next potential locations, based on probLoc
    nextLocs <- nextLocs[,.SD[findInterval(probLoc[id], cumsum(prob/sum(prob))) + 1],
                         by = id, .SDcols = c("x", "y", "prob")]
    selectedLocID <- as.matrix(nextLocs)[,c(2,3,1), drop = FALSE]

Do you have an idea on why this happens? I first thought cumsum() might get too large, but prints of it seemed fine to me. 

Thank you for any advice :)

Clara

[C M]

So I always get

Error in findInterval(probLoc[id], cumsum(prob/sum(prob))) : 

  'vec' must be sorted non-decreasingly and not contain NAs 

Do you think:

 1) Choosing MeanPixelQuality = 0.94 instead of 0.84. is invalid? And thus this error is not a problem? Since there are only very few raster cells with habitatsuitability >= 0.94. 

or 

 2) it is a valid choice and should just result in a strong barrier effect of any but the best habitat suitability, leading to long searches with therefore high mortality?

The latter is what I think should happen, but I might be wrong. Shouldn't there be a criterium that the doubling of steplength only can happen maybe 3-4 times, and if this doesn't result in any suitable cell the disperser dies? I am not at all sure, but I think the error might occur because of indefinite doubling of steplength. 

[C M]

A dirty fix would be this:

https://github.com/USGS-R/EflowStats/issues/155

so I changed line 634 to

nextLocs <- nextLocs[,.SD[findInterval(probLoc[id], sort (cumsum(prob/sum(prob)))) + 1],

by = id, .SDcols = c("x", "y", "prob")]

Now it seems to run further,  even though cumsum should already be non-decreasing on its own. 

[sarah.b...@gmail.com]

Hi Clara,

Do you use the version currently on GitHub or a version a bit modified? Because I downloaded the wolfAlps module on GitHub and ran it a few times by modifying only MeanPixelQuality to 0.94 and I don't have any error.

Sarah