Python/C2/Using-the-plot-command-interactively/English-timed

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, lets 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 dropdown.
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, lets 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