* Script

**********

Some greeting-- Hi or Hello or Welcome - would be polite to start with

**********

For this we shall use  Ipython and pylab. 

Ipython is An Enhanced Interactive Python interpreter. It provides additional features like tab completion,easier access to help , and many other useful features.

Pylab is python library which provides plotting functionality. 

I am assuming that you have both Ipython and Pylab installed on your system .

$ ipython -pylab

press RETURN

We will first start with the absolute basic i.e how to print hello world

In []: print 'hello world'

$ ipython -pylab

press RETURN

In []: x = linspace(0, 2*pi, 50)

To obtain the plot we say,

In []: plot(x, sin(x))

***

As you can see a plot has appeared on the screen. 

***

The plot has the default color and line properties. 

In []: xla<TAB>bel('x') will add a label to the x-axis. Note that 'x' is enclosed in quotes. 

Similarly

In []: ylabel('sin(x)') adds a label to the y-axis.

To add a title to plot we simply use 

In []: tit<TAB>le('Sinusoid').

In []: legend(['sin(x)'])

To go to previous command, we can use 'UP Arrow key' and 'DOWN' will take us (in reverse order)/back.

We can modify previous command to specify the location of the legend, by passing an additional argument to the function. 

In []: legend(['sin(x)'], loc = 'center')

other positions which can be tried are

'best' 

'right'

In []: annotate('origin', xy=(0, 0))

The first argument is the comment string and second one is the position for it. 

In []: savefig('sin.png') saves the figure with the name 'sin.png' in the current directory. 

#other supported formats are: eps, ps, pdf etc.

When we use plot again by default plots get overlaid.

In []: plot(x, cos(x))

we update Y axis label 

In []: ylabel('f(x)')

Now in these situations with overlaid graphs, legend becomes absolutely essential. To add multiple legends, we pass the strings within quotes separated by commas and enclosed within square brackets as shown.

In []: legend( [ 'sin(x)' , 'cos(x)'] )

In []: clf()

clears the plot area and starts afresh.

The figure command is used to open a plain figure window without any plot.

In []: figure(1)

In []: plot(x, sin(x))

In []: figure(2)

figure() is also used to shift the focus between multiple windows. 

In []: plot(x, cos(x))

The previous plot window remains unchanged to these commands.

In []: figure(1)

title() sets the title of figure(1) 

In []: title('sin(x)')

In []: savefig('sine.png')

close() closes figure(1). Now there is just one figure that is open and hence 

the focus is automatically shifted to figure(2).

In []: close()

close() now closes the figure(2).

In []: close()

Passing the linewidth=2 option to plot, generates the plot with linewidth of two units.

Use Up arrow to get to the previous commands 

In []: plot(x, sin(x), 'g', linewidth=2) and add arguments

In []: clf()

In order to plot points you may pass '.' as a parameter to plot

In []: plot(x, sin(x), '.')

In []: clf()

In order to plot filled circles in black color you can pass 'ko' parameter to plot

In []: plot(x, cos(x), 'ko')

In []: clf()

A plot using dashed lines can be generated by passing the '--' parameter

In []: plot(x, sin(x), '--')

In []: clf()

and finally to close the plot

In []: close()

****************

This brings us to the end of this tutorial.  Thank you for attending this first tutorial on Python for Scientific Computing 

****************