Archived:How to plot a graph using PySymbian

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21 Sep
2009

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Aquivado: Este artigo foi arquivado, pois o conteúdo não é mais considerado relevante para se criar soluções comerciais atuais. Se você achar que este artigo ainda é importante, inclua o template {{ForArchiveReview|escreva a sua justificativa}}.

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Article Metadata

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Tested with

Devices(s): Nokia N96

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Compatibility

Platform(s): S60 2nd Edition, S60 3rd Edition

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Article

Keywords: graphics

Created: cyke64 (29 Mar 2007)

Last edited: hamishwillee (08 May 2013)

Overview

There's no easy way like matplotlib for plotting simple graphs in Python. So we need to manually create functions which draw graphs. Following code shows one of the possible ways.

Code

Graph functions

from __future__ import generators
from appuifw import *
 
def arange(start, stop=None, step=None):
    if stop is None:
        stop = float(start)
        start = 0.0
    if step is None:
        step = 1.0
    cur = float(start)
    while cur < stop:
        yield cur
        cur += step
 
# define application body
app.body = canvas = Canvas()
width, height = canvas.size  # get canvas size to scale graphs
 
# draw x and y axis
def axes(xyrange, position=[18, height-11, width-10, 10], formatter=lambda x:x):
    global left, bottom, right, top, min_x, min_y, scale_x, scale_y
    left, bottom, right, top = position
    min_x, max_x, step_x, min_y, max_y, step_y = xyrange
    scale_x = float(right-left)/(max_x-min_x)
    scale_y = float(bottom-top)/(max_y-min_y)
    canvas.clear()
    # draw axis rectangle(see images below)
    canvas.rectangle([(left,top), (right+1, bottom+1)], 0)
    # define points on axis and write numbers
    for x in arange(min_x, max_x, step_x):
        canvas.text((14+scale_x*(x-min_x), height-1), unicode(formatter(x)))
        canvas.point((left+scale_x*(x-min_x), bottom-1), 0)
        canvas.point((left+scale_x*(x-min_x), top+1), 0)
    for y in arange(min_y, max_y, step_y):
        canvas.text((2, bottom+2-scale_y*(y-min_y)), unicode(formatter(y)))
        canvas.point((left+1, bottom-scale_y*(y-min_y)), 0)
        canvas.point((right-1, bottom-scale_y*(y-min_y)), 0)
 
# plot co-ordinates and generate graph
def plot(xs, ys=None):
    if ys==None:
        ys = xs
        xs = range(len(ys))
    last = left+(xs[0]-min_x)*scale_x, bottom-(ys[0]-min_y)*scale_y
    for i in range(1, len(ys)):
        p = left+(xs[i]-min_x)*scale_x, bottom-(ys[i]-min_y)*scale_y
        canvas.line([last, p], 0x00000ff)
        last = p
    canvas.point(last, 0x0000ff)

Example Usage

When we want to plot a graph, we called both axes() and plot()

# a straight line
>>> axes([0,3.1,.5, 1,4.1,.5])
>>> plot([1,2,3,4])
 
# a parabola y = x^2
>>> axes([1,4.1,1, 0,16.1,2], formatter=int)
>>> plot([1,2,3,4], [1,4,9,16])

Postconditions

Following screenshots show the result of above code.

Straight Line

Parabola