I would like to cumulatively sum rows in a matrix, in which each row has 1
NA value.  The usual "na.rm=TRUE" does not seem to work with the command
cumsum.  Is there another way to ignore the NAs or do I need to figure out a
different way to do this?

Here's an example matrix of title "proportion":

        Ntrail    Strail      NFJD     Baldy     Onion      Crane
[1,]        NA 0.2944937 0.1779969 0.1808015 0.2296511 0.11705683
[2,] 0.2882713        NA 0.1795668 0.1823961 0.2316766 0.11808925
[3,] 0.1716890 0.1769419        NA 0.3518116 0.2025204 0.09703714
[4,] 0.1726311 0.1779128 0.3482548        NA 0.2036317 0.09756961
[5,] 0.2252904 0.2321833 0.2059743 0.2092197        NA 0.12733223
[6,] 0.2052614 0.2115415 0.1764081 0.1791877 0.2276013         NA

I want cumulative sums for each row.
Here's the code that works until it reaches an NA, then returns all
subsequent values as NA.  Adding na.rm=TRUE returns the error:
Error in FUN(newX[, i], ...) :  2 arguments passed to 'cumsum' which
requires 1

cumsums <- apply(proportion, 1, cumsum)

Thank you,
Tracy

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