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Time Narration
00:00 Hello friends and welcome to the tutorial on creating simple plots using iPython.
00:06 I hope you have iPython running on your computer.
00:10 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.

00:20 Let's start ipython.
00:22 Open the terminal and type: ipython -pylab and hit Enter.
00:35 Pylab is a python library which provides plotting functionality.
00:39 It provides many other important mathematical and scientific functions.
00:43 After running IPython -pylab in the shell, you will see some information about 'ipython' and pylab followed by the In[1] prompt.
00:55 But, if you get an error like 'ERROR: matplotlib could NOT be imported! Starting normal IPython.'
01:02 then you will have to install the matplotlib and run this command again.
01:08 Now type: 'linspace' followed by a '?' mark in your ipython shell.
01:19 As the documentation says, it "returns 'num' evenly spaced samples, calculated over the interval 'start' and 'stop'".
01:29 To illustrate this, let's try to generate 100 points.
01:33 Type: linspace within brackets 1 comma 100 comma 100 and hit Enter.
01:47 As you can see, a sequence of numbers from 1 to 100 appears.
01:52 Now let's try to generate 200 points between 0 and 1.
01:57 we do that by typing linspace within brackets 0 comma 1 comma 200.
02:11 Here, 0 is the start, 1- the stop and 200- the number of points.
02:18 In linspace, the start and stop points can be integers, decimals or constants.
02:24 Let's try and get 100 points between minus 'pi' to 'pi'.
02:30 Here 'pi' is a constant defined by pylab.
02:34 Save this to the variable, say 'p'.
02:52 If we now type 'len' within brackets 'p', we will get the no. of points.
03:05 len function gives the no. of elements of a sequence.
03:11 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'.
03:50 We can save cos(p) to variable 'cosine' and then plot it using the plot function.
03:57 Now, to clear the plot, we use the clf closing brackets function.
04:19 This is done because, if we wish to make another plot, it will overlap the previous plot.
04:25 As we do not wish to clutter the area with overlaid plots, we just clear it with clf().
04:34 Now, let's try a 'sine plot'.
05:04 We can study the plot better on the plot window by using the various options available on it.
05:11 Let us have a look at these options.
05:14 As we can observe, moving the mouse pointer along the plot gives us the location of each point on the plot.
05:26 To the bottom left of the window, there are a few buttons.
05:30 The right most among them is for saving the file.
05:35 Just click on it and type the file name.
05:48 We will save the file by the name 'sin_curve' in 'pdf' format.
06:00 As you can see, we can specify the format of file from the drop-down.
06:05 Formats like png, eps, pdf, ps are available.
06:17 Left to the save button is the slider button by which we can specify the margins.
06:25 Left to this is the zoom button by which we can zoom into the plot.
06:30 Just specify the region to zoom into.
06:40 The button to the left of it can be used to move the axes of the plot.
06:50 The next two buttons with left and right arrow icons change the state of the plot and take it to the previous state it was in.
07:00 It more or less acts like the back and forward button in a browser.
07:06 The last one is home, referring to the initial plot.
07:13 Pause the video here, try out the following exercise and resume the video.
07:20 Plot (sin(x) into sin(x)) by x.
07:26 1. Save the plot by the sin square by x.pdf in pdf format.
07:33 Second one. Zoom and find the maxima.
07:37 3. Bring it back to initial position.
07:44 Now, let's revise quickly what we have learnt today-
07:49 To Study Ipython with pylab.
07:52 To Use the linspace function to create num equally spaced points in a region.
07:57 To Find the length of sequences using len function.
08:01 Plot mathematical functions using plot.
08:05 To clear drawing area using clf.
08:08 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.
08:23 Create 100 equally spaced points between minus pi by 2 and pi by 2?
08:31 Second one is- How do you clear a figure in ipython?
08:36 The third one- How do you find the length of a sequence?
08:43 And the answers are-
08:45 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.
09:03 Second one- We use clf closing bracket function to clear a figure.
09:11 Third one- len within brackets 'sequence_name' is the function used to find out the length of a sequence.
09:20 Hope you have enjoyed and found it useful.
09:24 Thank you!

Contributors and Content Editors

Gaurav, Minal, PoojaMoolya, Sandhya.np14, Sneha