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Archived:How to plot a graph using PySymbian

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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)

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 generatorsfrom 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 bodyapp.body = canvas = Canvas()width, height = canvas.size  # get canvas size to scale graphs # draw x and y axisdef 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 graphdef 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