**Narration**
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Hello friends and welcome to the tutorial on *creating simple plots using iPython*.
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I hope you have **iPython** running on your computer.
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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.

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