Skip to main content

syntax - Postfix Double Slash Notation with Multiple Parameters



Examples


A convenient shorthand that I use frequently is the "double slash" notation to string commands together. For example, I can write:


x - 1 + x^2 //TraditionalForm


And receive back:


x^2 + x - 1

Or another example:


(x - 1)(x + 2) //Expand //TraditionalForm

Yields:


x^2 + x - 2




However, I have never been able to find a way to input multiple arguments into a function using this notation. That is, I cannot call something like:


x^2 + 9x + 5, 3 //PolynomialMod

Obviously the above can easily be written as:


PolynomialMod[x^2 + 9x + 5, 3]

(but what's the fun in that?)


Question


Is there a way to input multiple parameters using the shorthand postfix operator?


See also: http://reference.wolfram.com/language/ref/Postfix.html




Answer



A lot of functions in MMA have default values for Optional Arguments, for Example Flatten. It can take Flatten[expr] which means Flatten[expr, Infinity]


Some functions don't have such option and you need to feed the Optional Arguments but you can go around by building your own function


for your example, you can do this kind of trick like this:


f[expr_, n_: 3] := PolynomialMod[expr, n]

now


x^2 + 9 x + 5 // f
2 + x^2


In this case you will have fixed value for Optional Arguments which is 3 and if you need to use this method with other value than 3 you need to change 3 in the definition of f above. However, an easy way to do it is as follows:


x^2 + 9 x + 5 // PolynomialMod[#, 3] &

Comments

Popular posts from this blog

plotting - Filling between two spheres in SphericalPlot3D

Manipulate[ SphericalPlot3D[{1, 2 - n}, {θ, 0, Pi}, {ϕ, 0, 1.5 Pi}, Mesh -> None, PlotPoints -> 15, PlotRange -> {-2.2, 2.2}], {n, 0, 1}] I cant' seem to be able to make a filling between two spheres. I've already tried the obvious Filling -> {1 -> {2}} but Mathematica doesn't seem to like that option. Is there any easy way around this or ... Answer There is no built-in filling in SphericalPlot3D . One option is to use ParametricPlot3D to draw the surfaces between the two shells: Manipulate[ Show[SphericalPlot3D[{1, 2 - n}, {θ, 0, Pi}, {ϕ, 0, 1.5 Pi}, PlotPoints -> 15, PlotRange -> {-2.2, 2.2}], ParametricPlot3D[{ r {Sin[t] Cos[1.5 Pi], Sin[t] Sin[1.5 Pi], Cos[t]}, r {Sin[t] Cos[0 Pi], Sin[t] Sin[0 Pi], Cos[t]}}, {r, 1, 2 - n}, {t, 0, Pi}, PlotStyle -> Yellow, Mesh -> {2, 15}]], {n, 0, 1}]

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}]

plotting - Mathematica: 3D plot based on combined 2D graphs

I have several sigmoidal fits to 3 different datasets, with mean fit predictions plus the 95% confidence limits (not symmetrical around the mean) and the actual data. I would now like to show these different 2D plots projected in 3D as in but then using proper perspective. In the link here they give some solutions to combine the plots using isometric perspective, but I would like to use proper 3 point perspective. Any thoughts? Also any way to show the mean points per time point for each series plus or minus the standard error on the mean would be cool too, either using points+vertical bars, or using spheres plus tubes. Below are some test data and the fit function I am using. Note that I am working on a logit(proportion) scale and that the final vertical scale is Log10(percentage). (* some test data *) data = Table[Null, {i, 4}]; data[[1]] = {{1, -5.8}, {2, -5.4}, {3, -0.8}, {4, -0.2}, {5, 4.6}, {1, -6.4}, {2, -5.6}, {3, -0.7}, {4, 0.04}, {5, 1.0}, {1, -6.8}, {2, -4.7}, {3, -1.