Skip to main content

Accurately distort graphics


I would like to accurately distort this plot of sin(x1/2) (and others like it) so that the wavelengths are evened out (ie - "inverse-square root" it).


enter image description here


I should like to do the same to "de-log" plots too.


I have no idea where to start though.



Answer




plt1 = Plot[Sin[Sqrt[x]], {x, 0, 1000}, ImageSize -> 400];

ticks = Ticks /. AbsoluteOptions[plt1, Ticks];
ticks = MapAt[#^(1/2) &, ticks, {{1, All, 1}}];
plotrange = PlotRange[plt1];
plotrange = MapAt[#^(1/2) &, plotrange, {1}];

plt2 = Graphics[plt1[[1]] /. Line[x_] :> Line[{#[[1]]^(1/2), #[[2]]} & /@ x],
PlotRange -> plotrange, Ticks -> ticks, plt1[[2]]];
Row[{plt1, plt2}]


enter image description here


Update: The approach above works without issue in Version 9.0.1.0 (Windows 8 64bit). Unfortunately it does not work in Version 10 because AbsoluteOptions stopped working as expected in Version 10. A work-around until the AbsoluteOptions glitch is fixed (hopefully in Version 10.0.1.0) is to specify the ticks directly:


ticksb = {{#^(1/2),#}&/@FindDivisions[{0,1000},{5}][[1]],Automatic};
plt2b = Graphics[plt1[[1]] /. Line[x_] :> Line[{#[[1]]^(1/2), #[[2]]} & /@ x],
PlotRange -> plotrange, Ticks -> ticksb, plt1[[2]]];
Row[{plt1, plt2b}]

enter image description here


Comments

Popular posts from this blog

functions - Get leading series expansion term?

Given a function f[x] , I would like to have a function leadingSeries that returns just the leading term in the series around x=0 . For example: leadingSeries[(1/x + 2)/(4 + 1/x^2 + x)] x and leadingSeries[(1/x + 2 + (1 - 1/x^3)/4)/(4 + x)] -(1/(16 x^3)) Is there such a function in Mathematica? Or maybe one can implement it efficiently? EDIT I finally went with the following implementation, based on Carl Woll 's answer: lds[ex_,x_]:=( (ex/.x->(x+O[x]^2))/.SeriesData[U_,Z_,L_List,Mi_,Ma_,De_]:>SeriesData[U,Z,{L[[1]]},Mi,Mi+1,De]//Quiet//Normal) The advantage is, that this one also properly works with functions whose leading term is a constant: lds[Exp[x],x] 1 Answer Update 1 Updated to eliminate SeriesData and to not return additional terms Perhaps you could use: leadingSeries[expr_, x_] := Normal[expr /. x->(x+O[x]^2) /. a_List :> Take[a, 1]] Then for your examples: leadingSeries[(1/x + 2)/(4 + 1/x^2 + x), x] leadingSeries[Exp[x], x] leadingSeries[(1/x + 2 + (1 - 1/x...

mathematical optimization - Minimizing using indices, error: Part::pkspec1: The expression cannot be used as a part specification

I want to use Minimize where the variables to minimize are indices pointing into an array. Here a MWE that hopefully shows what my problem is. vars = u@# & /@ Range[3]; cons = Flatten@ { Table[(u[j] != #) & /@ vars[[j + 1 ;; -1]], {j, 1, 3 - 1}], 1 vec1 = {1, 2, 3}; vec2 = {1, 2, 3}; Minimize[{Total@((vec1[[#]] - vec2[[u[#]]])^2 & /@ Range[1, 3]), cons}, vars, Integers] The error I get: Part::pkspec1: The expression u[1] cannot be used as a part specification. >> Answer Ok, it seems that one can get around Mathematica trying to evaluate vec2[[u[1]]] too early by using the function Indexed[vec2,u[1]] . The working MWE would then look like the following: vars = u@# & /@ Range[3]; cons = Flatten@{ Table[(u[j] != #) & /@ vars[[j + 1 ;; -1]], {j, 1, 3 - 1}], 1 vec1 = {1, 2, 3}; vec2 = {1, 2, 3}; NMinimize[ {Total@((vec1[[#]] - Indexed[vec2, u[#]])^2 & /@ R...

plotting - Plot 4D data with color as 4th dimension

I have a list of 4D data (x position, y position, amplitude, wavelength). I want to plot x, y, and amplitude on a 3D plot and have the color of the points correspond to the wavelength. I have seen many examples using functions to define color but my wavelength cannot be expressed by an analytic function. Is there a simple way to do this? Answer Here a another possible way to visualize 4D data: data = Flatten[Table[{x, y, x^2 + y^2, Sin[x - y]}, {x, -Pi, Pi,Pi/10}, {y,-Pi,Pi, Pi/10}], 1]; You can use the function Point along with VertexColors . Now the points are places using the first three elements and the color is determined by the fourth. In this case I used Hue, but you can use whatever you prefer. Graphics3D[ Point[data[[All, 1 ;; 3]], VertexColors -> Hue /@ data[[All, 4]]], Axes -> True, BoxRatios -> {1, 1, 1/GoldenRatio}]