elcojon's profile - activity

How do I convert a lambda function to a sage object?

I would like to use the plot command with my lambda function

from numpy import sign
H=lambda x: (sign(x)+1)/2
P = lambda x, a,b: H(x - a) - H(x - b)
plot(P(x,5,10), (x,-10,20)
# or 
BOX510(x) = lambda x: P(x,5,10)
plot(BOX510(x), (x,-10,20)

I get error messages. I had a glance at the documentation. It says the plot command expects a Sage Object, but unfortuntely I do not have the notion for its meaning.

Eureka, it works, when I use the sign function of sage instead of the one I imported from numpy. Yet, I would like to know what a sage object is?

it does not work! I tested it. It stops running with a TypeError. TypeError: 'Graphics3dGroup' object is not iterable

to whom may I send the patch to review it?

I modified my sage source code to do solve this for me. I had to modify matrix_plot.py.

Hello,

I am using matrix_plot to display my 2 dimensional array of data. Is there a way to change the tick mark values? Right now they are set to the index values of the matrix.

Also see this example from Matlab Stackoverflow

I was already trying to overload matplotlib keyword extent Example:

matrix_plot(mat, extent=[horLeft, horRight, verTop, verBottom])

This must be pretty new functionality, because in Sage 5.2

verbose 0 (138: primitive.py, options) WARNING: Ignoring option 'title'=Lena image

and indeed there is no title. In Sage 5.3 we have the following picture, as you point out.

And it looks like [#10512: Jason Grout, Punarbasu Purkayastha, Sébastien Labbé: wrap matplotlib's title functionality Reviewed by Sébastien Labbé, Punarbasu Purkayastha is what happened here - it adds the functionality, but didn't realize that with matrix_plot you will get stuff like this. But compare

sage: matrix_plot(data,axes_labels=piclabels, title='Lena image',origin='lower')

So I think that this will be pretty easy to fix by moving the title like we do for regular plots. I've opened Trac 13625 for this.

Wow, that was fast. And the trac ticket tells us that this is already reported to mpl upstream.

I am using matrix_plot to show an image. I would like to put a title on top of the plot. Unfortunately the result looks unsatisfactory. Is there a preferred way to put a title to matrix_plot?

piclabels = ('width [px]','height [px]')
import scipy 
data = scipy.lena()
matrix_plot(data,axes_labels=piclabels, title='Lena image')

Due to lack of karma, I cannot attach an image show that the title is overlapping with the axis.

You can do

import Image
img = Image.open(DATA+"filename") # if you load the image from disk
img = Image.fromarray(imgarray) # if the image is numpy array

img.save("test.png")

It will show up in the notebook. But it will also save a copy of the image to your disk. If I find out how to write the image to /dev/null, then maybe I could avoid writing to disk.