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Archived:How to plot a graph using PySymbian

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Archived.pngAquivado: 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
Tested with
Devices(s): Nokia N96
Compatibility
Platform(s): S60 2nd Edition, S60 3rd Edition
Article
Keywords: graphics
Created: cyke64 (29 Mar 2007)
Last edited: hamishwillee (31 May 2013)

Contents

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
This page was last modified on 31 May 2013, at 01:05.
36 page views in the last 30 days.

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