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

Timing	Visual Cue
0:00	Hello Friends and welcome to the tutorial on creating simple plots using iPython.
0:06	I hope you have IPython running on your computer.
0:10	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.
0:20	Lets start ipython.
0:22	Open the terminal and type ipython -pylab and hit enter.
0:35	Pylab is a python library which provides plotting functionality.
0:39	It provides many other important mathematical and scientific functions.
0:43	After running IPython -pylab in the shell you will see some information about ipython and pylab followed by the In[1] prompt.
0:55	But if you get an error like `ERROR: matplotlib could NOT be imported! Starting normal IPython.`
1:02	Then you will have to install the matplotlib and run this command again.
1:08	Now type 'linspace' followed by a '?' mark in your ipython shell
1:19	as the documentation says, it returns num evenly spaced samples, calculated over the interval start and stop.
1:29	To illustrate this, lets try to generate 100 points.
1:33	Type linspace within brackets 1 comma 100 comma 100 and hit enter.
1:47	As you can see a sequence of numbers from 1 to 100 appears.
1:52	Now lets try to generate 200 points between 0 and 1.
1:57	we do that by typing linspace within brackets 0 comma 1 comma 200.
2:11	Here,0 is the start , 1 the stop and 200 the number of points.
2:18	In linspace the start and stop points can be integers, decimals , or constants.
2:24	Let's try and get 100 points between minus pi to pi.
2:30	Here 'pi' is a constant defined by pylab.
2:34	Save this to the variable,say p.
2:52	If we now type len within brackets p we will get the no. of points.
3:05	len function gives the no of elements of a sequence.
3:11	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.
3:50	We can save cos(p) to variable cosine and then plot it using the plot function.
3:57	Now to clear the plot ,we use the clf closing brackets function
4:19	This is done because if we wish to make another plot, it will overlap the previous plot.
4:25	As we do not wish to clutter the area with overlaid plots , we just clear it with clf().
4:34	Now lets try a sine plot.
5:04	We can study the plot better on the plot window by using the various options available on it.
5:11	Let us have a look at these options.
5:14	As we can observe, moving the mouse pointer along the plot gives us the location of each point on the plot
5:26	To the bottom left of the window,there are a few buttons.
5:30	The right most among them is for saving the file.
5:35	Just click on it and type the file name.
5:48	We will save the plot by the name sin_curve in pdf format.
6:00	As you can see we can specify the format of file from the dropdown.
6:05	Formats like png ,eps ,pdf, ps are available.
6:17	Left to the save button is the slider button by which we can specify the margins.
6:25	Left to this is the zoom button by which we can zoom into the plot.
6:30	Just specify the region to zoom into.
6:40	The button to the left of it can be used to move the axes of the plot.
6:50	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.
7:00	It more or less acts like the back and forward button in a browser.
7:06	The last one is 'home' referring to the initial plot.
7:13	Pause the video here, try out the following exercise and resume the video.
7:20	Plot (sin(x) into sin(x)) by x.
7:26	1. Save the plot by the sin square by x.pdf in pdf format.
7:33	Second one. Zoom and find the maxima.
7:37	3. Bring it back to initial position.
7:44	Now, lets revise quickly what we have learnt today.
7:49	To Study Ipython with pylab.
7:52	To Use the linspace function to create num equally spaced points in a region.
7:57	To Find the length of sequences using len function.
8:01	Plot mathematical functions using plot.
8:05	To clear drawing area using clf.
8:08	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.
8:23	Create 100 equally spaced points between minus pi by 2 and pi by 2?
8:31	Second one is. How do you clear a figure in ipython?
8:36	The third one. How do you find the length of a sequence?
8:43	And the answers are,
8:45	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.
9:03	Second one. We use clf closing bracket function to clear a figure.
9:11	Third one. len within brackets sequence_name is the function used to find out the length of a sequence.
9:20	Hope you have enjoyed and found it useful.
9:24	Thank you!

Contributors and Content Editors

Gaurav, Minal, PoojaMoolya, Sandhya.np14, Sneha