On Sun, 23 Nov 2008 16:48:59 -0800 Zane Selvans <[EMAIL PROTECTED]> wrote:
> Incidentally, when you do it with ax.plot() instead you can see more > easily that the corners where the two sinusoidal functions intersect > are getting kind of chopped off by the polygon filling. Don't know if > there's an easy way to fix that - maybe by forcing the list of polygon > vertices to always explicitly include the points of intersection > between the functions being filled_between? Or maybe just by > increasing the number of vertices, though I assume that would slow > things down. Some time back, I wrote code to generate a fairly complex polyfill in a plot in R, http://www.oplnk.net/~ajackson/weather/Temperature_2000.png The key bit of code to find the intersections between all the curves to fill the corners correctly is here (note that this is "R" code): intersect <- function(a, b, c, d) { # test two line segments for intersection. # modified from segseg in "Computational Geometry in C" # by Joseph O'Rourke p = c(0,0) denom = a[1] * ( d[2] - c[2] ) + b[1] * ( c[2] - d[2] ) + d[1] * ( b[2] - a[2] ) + c[1] * ( a[2] - b[2] ); # If denom is zero, then segments are parallel: handle separately. if (abs(denom) <= 1.0e-10) { return (c(p,0)) } num = a[1] * ( d[2] - c[2] ) + c[1] * ( a[2] - d[2] ) + d[1] * ( c[2] - a[2] ); if ( (num == 0.0) || (num == denom) ) code = 0; s = num / denom; num = -( a[1] * ( c[2] - b[2] ) + b[1] * ( a[2] - c[2] ) + c[1] * ( b[2] - a[2] ) ); if ( (num == 0.0) || (num == denom) ) code = 0; t = num / denom; if ( (0.0 < s) && (s < 1.0) && (0.0 < t) && (t < 1.0) ) { code = 1; } else if ( (0.0 > s) || (s > 1.0) || (0.0 > t) || (t > 1.0) ) { code = 0; } p[1] = a[1] + s * ( b[1] - a[1] ); p[2] = a[2] + s * ( b[2] - a[2] ); c(p,code); } # Intersect two lines defined by a series of segments. Assume the # lines have common x-values and differ only in y # intersect is array of (x,y) values intersect.lines <- function (y1,y2,x) { intersect = array(data = NA, dim = c(2,0), dimnames = NULL) for (i in 2:length(x)) { a = c(x[i-1], y1[i-1]) b = c(x[i], y1[i]) c = c(x[i-1], y2[i-1]) d = c(x[i], y2[i]) foo = intersect(a,b,c,d) if (foo[3]) { intersect = cbind(intersect, foo[1:2]) } } intersect } -- ----------------------------------------------------------------------- | Alan K. Jackson | To see a World in a Grain of Sand | | [EMAIL PROTECTED] | And a Heaven in a Wild Flower, | | www.ajackson.org | Hold Infinity in the palm of your hand | | Houston, Texas | And Eternity in an hour. - Blake | ----------------------------------------------------------------------- ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
