raster stack/brick cor.test p-values

Dear list:

I am trying to get pixel-wise correlations and significance between two
raster bricks; one representing monthly NDVI means and another representing
monthly rainfall means.

I found the following two codes (both from Robert Hijmans) from a previous
discussions on this list:
http://r-sig-geo.2731867.n2.nabble.com/questions-on-RasterStack-Brick-td5553580.html
and
from StackOverflow:
http://stackoverflow.com/questions/16698048/r-calculating-pearson-correlation-coefficient-in-each-cell-along-time-line


# code 1

funcal <- function(xy) {
    xy <- na.omit(matrix(xy, ncol=2))
    if (ncol(xy) < 2) {
        NA
    } else {
        cor(xy[, 1], xy[, 2])
    }
}
s <- stack(sa, sb)
calc(s, funcal)
# code 2
stackcor <- function(s1, s2, method='spearman') {
        mycor <- function(v) {
                x <- v[1:split]
                y <- v[(split+1):(2*split)]
                cor(x, y, method=method)
        }
        s <- stack(s1, s2)
        split <- nlayers(s)/2
        calc(s, fun=mycor )
}

Both codes work as expected with the "cor" function, producing correlation
grids. However, I tried substituting the cor with cor.test in order to
extract the p-values:

# using the first code

funcal <- function(xy) {
    xy <- na.omit(matrix(xy, ncol=2))
    if (ncol(xy) < 2) {
        NA
    } else {
        cor.test(xy[, 1], xy[, 2],method="pearson")$p.value
    }
}
s <- stack(sa, sb)
calc(s, funcal)

I am met with the following error (with trackback in RStudio):

Error in cor.test.default(xy[, 1], xy[, 2], method = "pearson") :

  not enough finite observations
8 stop("not enough finite observations")
7 cor.test.default(xy[, 1], xy[, 2], method = "pearson")
6 cor.test(xy[, 1], xy[, 2], method = "pearson")
5 FUN(newX[, i], ...)
4 apply(v, 1, fun)
3 .local(x, fun, ...)
2 calc(meistack, brick.cor.pval)
1 calc(meistack, brick.cor.pval)

In the previous r-sig-geo, a user had asked about this error but it was
left unanswered. I was wondering if anyone can help with this?

Thanks!

Hakim