"A. Tsiolakidis" <tsioltas at cs.keele.ac.uk> writes:
> I am a total beginner with this whole thing so please have patience!
>
> I am trying to run an S-plus program with a certain line:
> spline(1:nrow(y), y[,1],n=100);
>
> This crashes with:
> Error: NAs in foreign function call (arg 8)
>
> Apparently, this is caused by the last command of spline:
> u <- seq(xmin, xmax, length.out = n)
> .C("spline_eval", z$method, length(u), x = u, y =
double(n),
> z$n, z$x, z$y, z$b, z$c, z$d)[c("x",
"y")]
> }
>
> Now, I can cause that error with: spline(1:10,1:10)
> So, there is a whole class of problems for which spline refuses to
> compute anything - is this the correct behaviour? E.g.,
> spline(1:10,(1:10)/2.5) #it is alright, but ...
> spline(1:10,(1:10)/2) # this has the "NAs.." problem
>
> Finally, I am almost sure that the y matrix in my program has quite
> normal values, i.e. values that should allow for meaningful
> interpolation.
> Anybody knows what this all is about?
If you have the splines library installed, could you try the same
problem using interpSpline instead of spline? The sequence for the
1:10, 1:10 example looks like
R> library(splines)
R> ttt <- interpSpline(y ~ x, data.frame(x = 1:10, y = 1:10) )
R> ttt
polynomial representation of spline for y ~ x
constant linear quadratic cubic
1 1 1 0.0000e+00 -3.3307e-16
2 2 1 -9.9920e-16 9.9920e-16
3 3 1 1.9984e-15 -1.4063e-15
4 4 1 -2.2204e-15 7.4015e-16
5 5 1 0.0000e+00 8.8818e-16
6 6 1 2.6645e-15 -1.7764e-15
7 7 1 -2.6645e-15 8.8818e-16
8 8 1 0.0000e+00 8.8818e-16
9 9 1 2.6645e-15 -8.8818e-16
10 10 1 0.0000e+00 -8.8818e-16
R> plot( ttt ) # produces a nice straight line plot.
R> predict( ttt )
$x
[1] 1.00 1.18 1.36 1.54 1.72 1.90 2.08 2.26 2.44 2.62
[11] 2.80 2.98 3.16 3.34 3.52 3.70 3.88 4.06 4.24 4.42
[21] 4.60 4.78 4.96 5.14 5.32 5.50 5.68 5.86 6.04 6.22
[31] 6.40 6.58 6.76 6.94 7.12 7.30 7.48 7.66 7.84 8.02
[41] 8.20 8.38 8.56 8.74 8.92 9.10 9.28 9.46 9.64 9.82
[51] 10.00
$y
[1] 1.00 1.18 1.36 1.54 1.72 1.90 2.08 2.26 2.44 2.62
[11] 2.80 2.98 3.16 3.34 3.52 3.70 3.88 4.06 4.24 4.42
[21] 4.60 4.78 4.96 5.14 5.32 5.50 5.68 5.86 6.04 6.22
[31] 6.40 6.58 6.76 6.94 7.12 7.30 7.48 7.66 7.84 8.02
[41] 8.20 8.38 8.56 8.74 8.92 9.10 9.28 9.46 9.64 9.82
[51] 10.00
attr(,"class")
[1] "xyVector"
R> predict( ttt, len = 100 )
Error in predict.npolySpline(ttt, len = 100) : unused argument to function
R> predict( ttt, nseg = 100 )
$x
[1] 1.00 1.09 1.18 1.27 1.36 1.45 1.54 1.63 1.72 1.81
[11] 1.90 1.99 2.08 2.17 2.26 2.35 2.44 2.53 2.62 2.71
[21] 2.80 2.89 2.98 3.07 3.16 3.25 3.34 3.43 3.52 3.61
[31] 3.70 3.79 3.88 3.97 4.06 4.15 4.24 4.33 4.42 4.51
[41] 4.60 4.69 4.78 4.87 4.96 5.05 5.14 5.23 5.32 5.41
[51] 5.50 5.59 5.68 5.77 5.86 5.95 6.04 6.13 6.22 6.31
[61] 6.40 6.49 6.58 6.67 6.76 6.85 6.94 7.03 7.12 7.21
[71] 7.30 7.39 7.48 7.57 7.66 7.75 7.84 7.93 8.02 8.11
[81] 8.20 8.29 8.38 8.47 8.56 8.65 8.74 8.83 8.92 9.01
[91] 9.10 9.19 9.28 9.37 9.46 9.55 9.64 9.73 9.82 9.91
[101] 10.00
$y
[1] 1.00 1.09 1.18 1.27 1.36 1.45 1.54 1.63 1.72 1.81
[11] 1.90 1.99 2.08 2.17 2.26 2.35 2.44 2.53 2.62 2.71
[21] 2.80 2.89 2.98 3.07 3.16 3.25 3.34 3.43 3.52 3.61
[31] 3.70 3.79 3.88 3.97 4.06 4.15 4.24 4.33 4.42 4.51
[41] 4.60 4.69 4.78 4.87 4.96 5.05 5.14 5.23 5.32 5.41
[51] 5.50 5.59 5.68 5.77 5.86 5.95 6.04 6.13 6.22 6.31
[61] 6.40 6.49 6.58 6.67 6.76 6.85 6.94 7.03 7.12 7.21
[71] 7.30 7.39 7.48 7.57 7.66 7.75 7.84 7.93 8.02 8.11
[81] 8.20 8.29 8.38 8.47 8.56 8.65 8.74 8.83 8.92 9.01
[91] 9.10 9.19 9.28 9.37 9.46 9.55 9.64 9.73 9.82 9.91
[101] 10.00
attr(,"class")
[1] "xyVector"
The splines library is available in the src/contrib section of any of
the CRAN archives. The master CRAN site is
http://www.ci.tuwien.ac.at/R/contents.html
--
Douglas Bates bates at stat.wisc.edu
Statistics Department 608/262-2598
University of Wisconsin - Madison http://www.stat.wisc.edu/~bates/
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !) To: r-help-request at
stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._