| 修订版 | f86ada8e26102d800f0da7be1ba831eb3dc67da7 (tree) |
|---|---|
| 时间 | 2007-12-03 19:41:45 |
| 作者 | iselllo |
| Commiter | iselllo |
I added the code plot-vector.R. It is taken from R mailing list and it
shows how to draw a vector field using R.
R-codes/plot-vector.R (diff)| @@ -0,0 +1,50 @@ | ||
| 1 | +### FUNCTION DEFINITION | |
| 2 | + | |
| 3 | +#! Outer product with vector function ### | |
| 4 | +# expand.outer joins functionality of "expand.grid" and "outer", so that | |
| 5 | +# a vector function can be applied, values of which are then stored in | |
| 6 | +# collumns. | |
| 7 | +# Combinations of "x" and "y" are expanded into vectors of length n*m, | |
| 8 | +# where | |
| 9 | +# n = length(x), m = length(y) and this ordering is preserved also in | |
| 10 | +#'values'. | |
| 11 | +# Matrix of values (list item 'values') and expanded variables (list | |
| 12 | +#items 'x','y') are returned. | |
| 13 | + | |
| 14 | +expand.outer <- function(x, y, vecfun) { | |
| 15 | +xy.pairs <- expand.grid(x=x, y=y, KEEP.OUT.ATTRS = FALSE) | |
| 16 | +x.exp <- xy.pairs$x | |
| 17 | +y.exp <- xy.pairs$y | |
| 18 | +list(values=matrix(vecfun(x.exp,y.exp), nrow=2, byrow=TRUE), x=x.exp, | |
| 19 | +y=y.exp) | |
| 20 | +} | |
| 21 | + | |
| 22 | +#! vector field plot function | |
| 23 | +# grid.points can be defined for both axes at once or separately | |
| 24 | + | |
| 25 | +plotVectorField <- function(vecfun, xlim, ylim, grid.points) { | |
| 26 | +gp <- if(length(grid.points)>1) grid.points else rep(grid.points,2) | |
| 27 | +maxlength <- c(diff(xlim),diff(ylim))/(gp-1)*0.9 | |
| 28 | +#prepare data | |
| 29 | +x0 <- seq(xlim[1], xlim[2], length=gp[1]) | |
| 30 | +y0 <- seq(ylim[1], ylim[2], length=gp[2]) | |
| 31 | +xy.data <- expand.outer(x0, y0, vecfun) | |
| 32 | +x0 <- xy.data$x | |
| 33 | +y0 <- xy.data$y | |
| 34 | +dx <- xy.data$values[1,] | |
| 35 | +dy <- xy.data$values[2,] | |
| 36 | +#scale | |
| 37 | +k <- min( maxlength / c(max(abs(dx)),max(abs(dy))) ) | |
| 38 | +x1 <- x0 + k*dx | |
| 39 | +y1 <- y0 + k*dy | |
| 40 | +#plot | |
| 41 | +plot.default(range(x0,x1), range(y0,y1), main="Vector field", xlab="", | |
| 42 | +ylab="", type="n", frame.plot=F) | |
| 43 | +arrows(x0,y0,x1,y1,length = 0.08, angle = 20, code = 2) | |
| 44 | +} | |
| 45 | + | |
| 46 | +### FUNCTION CALL | |
| 47 | + | |
| 48 | +plotVectorField(function(x1,x2) c(x2,-x1), c(-1,1), c(-1,1), 9) | |
| 49 | + | |
| 50 | + |
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