Difference between revisions of "Python/C2/Using-the-plot-command-interactively/English-timed"

| Hello Friends and welcome to the tutorial on ''creating simple plots using iPython''.

| I hope you have, IPython running on your computer.

| At the end of this tutorial, you will be able to,

 

# Create simple plots of mathematical functions.

# Use the Figure window to study plots better.

| Lets start'' ipython''.

| Open the terminal and type ''ipython -pylab'' and hit enter.

| ''Pylab'' is a python library which provides plotting functionality.

| After running, IPython -pylab in the shell you will see some information about ipython and pylab followed by the ''In[1] prompt''

| But if you get an error like `ERROR: ''matplotlib'' could NOT be imported!  Starting normal IPython.`

|Then you will have to install the ''matplotlib ''and run this command again.

| Now type 'linspace' followed by a '?' mark in your ipython shell

| as the documentation says, it returns ''num'' evenly spaced samples, calculated over the interval start and stop.

| To illustrate this, lets try to generate ''100 points''.

| Type <tt>linspace within brackets ''1 comma 100 comma 100'' </tt> and hit enter.

| As you can see a sequence of numbers from ''1 to 100 appears.

| Now lets try to generate'' 200 points between 0 and 1''.

|we do that by typing'' linspace'' within brackets ''0 comma 1 comma 200''.

| Here,''0'' is the start , 1 the stop and 200 the number of points.

| In linspace the start and stop points can be integers, decimals , or constants.  

|Let's try and get ''100 points between  minus pi to pi''.

| Here 'pi' is a constant defined by ''pylab''.

| Save this to the variable,say ''p''.

| If we now type ''len'' within brackets ''p'' we will get the no. of points.

| ''len'' function gives the no of elements of a sequence.

| Let's try and plot a cosine curve between minus pi and pi. For this we use the plot command. Here ''cos(p)'' gets the cosine value at every point corresponding to point p.

| We can save ''cos(p)'' to variable cosine and then plot it using the plot function.

| Now to clear the plot ,we use the ''clf'' closing brackets function

| This is done, because if we wish to make another plot, it will overlap the previous plot.

| As we do not wish to clutter the area with overlaid plots , we just clear it with ''clf()''.  

|Now, lets try a sine plot.

| We can study the plot better on the plot window by using the various options available on it.

| As we can observe, moving the mouse pointer along the plot gives us the location of each point on the plot

| To the bottom left of the window,there are a few buttons.  

|We will save the file  by the name ''sin_curve'' in pdf format.

| As you can see we can specify the format of file from the ''dropdown''.  

|Formats like'' png ,eps ,pdf, ps'' are available.

| Left to the save button is the slider button by which we can specify the margins.

| Left to this is the zoom button by which we can zoom into the plot.

| The last one is 'home' referring to the initial plot.

|Plot ''(sin(x) into sin(x))'' by x.

| 1. Save the plot by the sin square by ''x.pdf ''in pdf format.

| Second one. ''Zoom'' and find the'' maxima''.

| Now, lets revise quickly what we have learnt today.

|To Study ''Ipython'' with ''pylab''.

| To Use the ''linspace ''function to create ''num'' equally spaced points in a region.

|To Find the length of sequences using ''len'' function.

| ''Plot'' mathematical functions using plot.

| To clear drawing area using ''clf''.

| To Use the'' UI'' of plot for studying it better and using functionality like save,zoom and moving the plots on ''x and y axis''.

| Create 100 equally spaced points between minus pi by'' 2 and pi by 2?''

|Second one is. How do you clear a figure in'' ipython?''

|The third one. How do you find the length of a sequence?

| And the answers are,

|1.We use the command ''linspace within brackets minus pi by ''2 comma pi by 2 comma 100'' to create 100 equally spaced lines between the points minus pi by 2 and pi by 2''.

|Second one. We use'' clf ''closing bracket function to clear a figure.

|Third one. ''len within brackets sequence_name'' is the function used to find out the length of a sequence.