Re: [julia-users] Re: Meshgrid in Julia: a working example and possible alternatives
julia include(plotnan.jl) INFO: Loading help data... /Users/dss/anaconda/lib/python2.7/site-packages/matplotlib/colors.py:583: RuntimeWarning: invalid value encountered in less cbook._putmask(xa, xa 0.0, -1) PyObject matplotlib.collections.PolyCollection object at 0x11993b4d0 This is the code: using PyPlot x = rand(8,8) x[1] = NaN pcolor(x) On Wednesday, November 26, 2014 8:05:32 AM UTC-6, Steven G. Johnson wrote: On Wednesday, November 26, 2014 12:45:09 AM UTC-5, David Smith wrote: My up-to-date version of Matplotlib won't plot NaNs either. That's weird; it works fine for me in Matplotlib 1.4.0. In any case, you can always zero out the NaN values in W via: W[isnan(W)] = 0 before plotting.
Re: [julia-users] Re: Meshgrid in Julia: a working example and possible alternatives
Sorry, forgot the version. That was matplotlib1.4.0np19py27_0
Re: [julia-users] Re: Meshgrid in Julia: a working example and possible alternatives
On Wednesday, November 26, 2014 12:45:09 AM UTC-5, David Smith wrote: My up-to-date version of Matplotlib won't plot NaNs either. That's weird; it works fine for me in Matplotlib 1.4.0. In any case, you can always zero out the NaN values in W via: W[isnan(W)] = 0 before plotting.
Re: [julia-users] Re: Meshgrid in Julia: a working example and possible alternatives
I found out that the code works when I use IJulia, but not when I run the command: julia file.jl. This is weird indeed ... Τη Τετάρτη, 26 Νοεμβρίου 2014 9:05:32 π.μ. UTC-5, ο χρήστης Steven G. Johnson έγραψε: On Wednesday, November 26, 2014 12:45:09 AM UTC-5, David Smith wrote: My up-to-date version of Matplotlib won't plot NaNs either. That's weird; it works fine for me in Matplotlib 1.4.0. In any case, you can always zero out the NaN values in W via: W[isnan(W)] = 0 before plotting.
[julia-users] Re: Meshgrid in Julia: a working example and possible alternatives
Also consider using for loops to eliminate the need for storage of intermediates. For loops are much faster in Julia than in Matlab. On Tuesday, November 25, 2014 2:26:39 PM UTC-6, Peter Simon wrote: You can find examples of both meshgrid and ndgrid implemented in https://github.com/JuliaLang/julia/blob/master/examples/ndgrid.jl . However, you will find that generally meshgrid is not needed, as similar functionality can be accomplished by broadcasting http://docs.julialang.org/en/release-0.3/manual/arrays/?highlight=broadcast#broadcasting or by use of comprehensions http://docs.julialang.org/en/release-0.3/manual/arrays/?highlight=broadcast#comprehensions . --Peter On Tuesday, November 25, 2014 11:39:57 AM UTC-8, Pileas wrote: Hi brothers, I am practicing a little bit in Julia now, and I want to see how meshgrid (if there is any) works. I found an example in Matlab (for I find it easier to cope with and make it Julia compatible), but I don't know how to do the meshgrid. Here is the example: -- col = 20; m = 400; cx = -.6; cy = 0; l = 1.5; x = linspace(cx-l,cx + l,m); y = linspace(cy-l,cy + l,m); (X,Y) = ndgrid(x,y); Z = zeros(m); C = X + i * Y; for k = 1:col; Z = Z.^2+C; W = exp(-abs(Z)); end colormap copper(256); pcolor(W); shading flat; axis(’square’,’equal’,’off’); - I would really appreciate if someone can give a working example in Julia of the aforementioned. Best ...
[julia-users] Re: Meshgrid in Julia: a working example and possible alternatives
Here is my solution, there is one problem that i do not understand and hope another can explain. When col=20 W is filled with NaN + NaN*im but for col=10 it work like matlab, I think it is because of overflow. using PyPlot col = 10; m = 400; cx = -.6; cy = 0; l = 1.5; x = linspace(cx-l,cx + l,m); y = linspace(cy-l,cy + l,m); X = repmat(x,1,m) Y = repmat(y,1,m)' Z = zeros(m,m); C = X + im * Y; W = zeros(Z) for k = 1:col; Z = Z.*Z+C W = exp(-abs(Z)); println(Z[100,100]) end pcolor(W,cmap=ColorMap(copper)) By changing the calculation to happen with BigFloats it works. Z = zeros(BigFloat, m,m); pcolor(float64(W),cmap=ColorMap(copper))
[julia-users] Re: Meshgrid in Julia: a working example and possible alternatives
Note that you don't need to use meshgrid, repmat, or similar, because you can use broadcasting operations (e.g .+) to combine row and column vectors: col = 20; m = 400; cx = -.6; cy = 0; l = 1.5; x = linspace(cx-l,cx + l,m); y = linspace(cy-l,cy + l,m); Z = zeros(m,m); C = x' .+ im * y; for k = 1:col; Z = Z.^2+C; end W = exp(-abs(Z)); pcolor(W, cmap=copper); colorbar() axis(equal) (Note also that there are more efficient ways to do this in Julia because you aren't forced to rely on vectorized operations, which allocate lots of temporary arrays, in order to get good performance.)
Re: [julia-users] Re: Meshgrid in Julia: a working example and possible alternatives
it does not understand pcolor, even when I load PyPlot. Why? Do we need to load a different package? 2014-11-25 15:59 GMT-05:00 Steven G. Johnson stevenj@gmail.com: Note that you don't need to use meshgrid, repmat, or similar, because you can use broadcasting operations (e.g .+) to combine row and column vectors: col = 20; m = 400; cx = -.6; cy = 0; l = 1.5; x = linspace(cx-l,cx + l,m); y = linspace(cy-l,cy + l,m); Z = zeros(m,m); C = x' .+ im * y; for k = 1:col; Z = Z.^2+C; end W = exp(-abs(Z)); pcolor(W, cmap=copper); colorbar() axis(equal) (Note also that there are more efficient ways to do this in Julia because you aren't forced to rely on vectorized operations, which allocate lots of temporary arrays, in order to get good performance.)
Re: [julia-users] Re: Meshgrid in Julia: a working example and possible alternatives
On Tuesday, November 25, 2014 4:05:58 PM UTC-5, Pileas wrote: it does not understand pcolor, even when I load PyPlot. Why? Do we need to load a different package? No. Maybe you don't have Matplotlib installed. (I would generally recommend using the Anaconda Python distro, which will include everything you might need, including IPython for running IJulia.)
Re: [julia-users] Re: Meshgrid in Julia: a working example and possible alternatives
I get the following error: /usr/lib/pymodules/python2.7/matplotlib/colorbar.py:581: RuntimeWarning: invalid value encountered in greater inrange = (ticks -0.001) (ticks 1.001) And I have Anaconda installed. Τη Τρίτη, 25 Νοεμβρίου 2014 4:59:22 μ.μ. UTC-5, ο χρήστης Steven G. Johnson έγραψε: On Tuesday, November 25, 2014 4:05:58 PM UTC-5, Pileas wrote: it does not understand pcolor, even when I load PyPlot. Why? Do we need to load a different package? No. Maybe you don't have Matplotlib installed. (I would generally recommend using the Anaconda Python distro, which will include everything you might need, including IPython for running IJulia.)
Re: [julia-users] Re: Meshgrid in Julia: a working example and possible alternatives
On Tuesday, November 25, 2014 9:26:31 PM UTC-5, Pileas wrote: I get the following error: /usr/lib/pymodules/python2.7/matplotlib/colorbar.py:581: RuntimeWarning: invalid value encountered in greater inrange = (ticks -0.001) (ticks 1.001) And I have Anaconda installed. Maybe, like the error says, you have an invalid value -- something in your array that is not a number, for example. For example, try pcolor(rand(10,10)) which should work.
Re: [julia-users] Re: Meshgrid in Julia: a working example and possible alternatives
(Note that the example code for the Mandelbrot set above produces an array containing NaN values. Maybe that doesn't work if you have an old version of Matplotlib. Maybe try doing a conda update etc. to be sure you have a recent version?)
Re: [julia-users] Re: Meshgrid in Julia: a working example and possible alternatives
My up-to-date version of Matplotlib won't plot NaNs either. On Tuesday, November 25, 2014 10:22:22 PM UTC-6, Steven G. Johnson wrote: (Note that the example code for the Mandelbrot set above produces an array containing NaN values. Maybe that doesn't work if you have an old version of Matplotlib. Maybe try doing a conda update etc. to be sure you have a recent version?)
