Difference between revisions of "Python/C2/Embellishing-a-plot/English-timed"
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Revision as of 16:16, 2 January 2013
| Timing | Narration |
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| 0:00 | Welcome to the tutorial on "Embellishing a Plot". |
| 0:06 | At the end of this tutorial, you will be able to,
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| 0:27 | So, Before beginning this tutorial,we would suggest you to complete the tutorial on "Using plot interactively". |
| 0:34 | so,let us start ipython with pylab loaded, open the terminal and type ipython hyphen pylab. |
| 0:48 | We shall first make a simple plot and start decorating it. |
| 0:54 | So type x is equal to linspace within brackets -2,4,20 |
| 1:06 | then type plot(x,sin(x)) |
| 1:15 | As we can see, the default colour and the default thickness of the line is as decided by pylab. |
| 1:23 | Wouldn't it be nice if we could control these parameters in the plot? |
| 1:28 | This is possible by passing additional arguments to the plot command. |
| 1:33 | We shall first clear the figure and plot the same by passing the additional color argument. |
| 1:39 | Pass the argument 'r' for red color. |
| 1:44 | So type clf, then plot within brackets x,sin(x),within single quotes r. |
| 2:13 | The same plot is seen in red color. |
| 2:16 | The thickness of the line can be altered by 'linewidth' argument. |
| 2:20 | So type plot within brackets x,cos(x),linewidth is equal to 2 |
| 2:34 | Now, a plot with line thickness 2 is produced. |
| 2:40 | Pause the video and do this exercise and then resume the video. |
| 2:45 | Plot sin(x) in blue color along with linewidth as 3. |
| 2:53 | So, now switch to terminal for solution A combination of color and linewidth would do the job for us. |
| 3:01 | So , type clf , then type plot within brackets x, sin(x),within single quotes b,linewidth is equal to 3. |
| 3:16 | To get the style of line as bunch of points not joined, pass the linestyle argument with or without color argument. |
| 3:25 | So for that type on the terminal clf, then type plot x,sin(x),within single quotes dot. |
| 3:43 | We get a plot with only points. |
| 3:49 | To get the same plot in blue color type clf, then type plot within brackets x, sin(x),within single quotes b dot. |
| 4:02 | Other available options for passing arguments can be seen in the documentation of plot. |
| 4:07 | For that , you can type in the terminal plot then question mark. |
| 4:19 | So, you can actually go through the documentation.
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| 4:23 | So , you pause the video and do this exercise and then resume the video. |
| 4:28 | Plot the sine curve with green filled circles. |
| 4:33 | so ,for solutionNow, switch to terminal . We use a combination of linestyle and color. |
| 4:40 | So ,type clf() then type plot within brackets x,cos(x), within single quotes go. |
| 4:56 | So, Pause the video here, try out the following exercise and resume the video. |
| 5:02 | Plot the curve of x versus tan(x) in red dash line and linewidth 3. |
| 5:13 | So for solution, we will switch to terminal . |
| 5:18 | Here we shall use a combination of linewidth argument and linestyle. |
| 5:22 | So in terminal you can type clf() then plot within brackets x, cos(x), within single quotes r hyphen hyphen |
| 5:36 | Now that we know how to produce a bare minimum plot with color, style and thickness of our interest, we shall look at further decorating the plot. |
| 5:46 | Let us start with a plot for the function minus x squared plus 4x minus 5. |
| 5:52 | So for that you have to type clf then plot within brackets x,minus x star x plus 4 star x minus 5,'r',linewidth is equal to 2. |
| 6:16 | As you can see, the figure does not have any description describing the plot. |
| 6:21 | To add a title to the plot to describe what the plot is,use the title command. |
| 6:26 | So, we can type in the terminal title within brackets and double quotes Parabolic function - x squared plus 4x minus 5 |
| 6:42 | The figure now has a title. |
| 6:45 | But it is not formatted and does not look clean. |
| 6:49 | It would look shabby if there were fractions and more complex functions like log and exp. |
| 6:57 | So, Wouldn't it be good if the title is seen in LaTeX like formatting? |
| 7:03 | This is possible by adding a $ sign before and after the part of the string that should be in LaTeX style. |
| 7:10 | So in the command you can type title within brackets and double quotes Parabolic function dollar sign minus x squared plus 4x minus 5 dollar sign
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| 7:26 | As we can see, the polynomial is now formatted. |
| 7:30 | Pause the video here, try out the following exercise and resume the video. |
| 7:35 | Change the title of the figure such that the whole title is formatted in LaTeX style. |
| 7:41 | Switch to terminal for solution. |
| 7:45 | The solution is to enclose the whole string in between $. |
| 7:51 | So you can type title within brackets dollar sign Parabolic function -x squared plus 4x minus 5 dollar sign. |
| 8:01 | Although we have title, the plot is not complete without labelling x and y axes. |
| 8:05 | we shall label x-axis to "x" and y-axis to "f(x)". |
| 8:12 | So for that you can type in terminal xlabel within brackets in double quotes x , then in terminal ylabel within brackets in double quotes f of x. |
| 8:31 | As you can see, xlabel and 'ylabel' command takes a string as an argument. |
| 8:37 | xlabel sets the label to x-axis as 'x' and ylabel sets the name to the y-axis as 'f(x)'.
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| 8:50 | Pause the video here, try out the following exercise and resume the video. |
| 8:57 | Set the x and y labels as "x" and "f(x)" in LaTeX style. |
| 9:04 | Since we need LaTeX style formatting, all we have to do is enclose the string in between two $. |
| 9:10 | Switch to terminal for solution and type xlabel within brackets dollar sign x dollar sign.
ylabel within brackets and double quotes dollar sign f of x dollar sign.
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| 9:31 | The plot is now almost complete except that the points are not named. |
| 9:37 | For example the point (2, -1) is the local maxima. |
| 9:42 | We would like to name the point accordingly. |
| 9:47 | To do this use the function annotate. |
| 9:49 | So for that you can type in the terminal annotate within brackets in double quotes local maxima comma xy is equal to within brackets 2 comma -1. |
| 10:04 | As you can see, the first argument to annotate command is the name we would like to mark the point as, and the second argument is the co-ordinates of the point at which the name should appear. |
| 10:18 | It is a tuple containing two numbers. |
| 10:20 | The first is x co-ordinate and second is y co-ordinate. |
| 10:25 | Pause the video, do this exercise and then resume the video. |
| 10:30 | Make an annotation called "root" at the point (-4, 0). |
| 10:38 | What happens to the first annotation ? |
| 10:43 | Switch to the terminal for the solution. |
| 10:46 | As we can see, every annotate command makes a new annotation on the figure. |
| 10:52 | Now we have everything we need to decorate a plot, but the plot would be incomplete if we can not set the limits of axes. |
| 11:01 | This can be done using the button provided on the plot window. |
| 11:06 | Else limits also can be get and set from the terminal. |
| 11:13 | Use "xlim()" and "ylim()" functions to get the limits. |
| 11:17 | So type in the terminal annotate within brackets in double quotes root comma xy is equal to within brackets minus 4 comma 0. |
| 11:32 | xlim function returns the current x axis limits and ylim function returns the current y-axis limits. |
| 11:41 | Set the limits of x-axis from -4 to 5 by giving command xlim(-4,5). |
| 12:12 | Similarly set the limits of y-axis appropriately. |
| 12:22 | Pause the video, do this exercise and then resume the video. |
| 12:27 | Set the limits of axes such that the area of interest is the rectangle (-1, -15) and (3, 0) |
| 12:37 | Switch to the terminal for the solution.
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| 12:40 | As we can see, the lower and upper limits of x-axis in the exercise are -1 and 3 respectively. |
| 12:46 | The lower and upper limits of y-axis are -15 and 0 respectively. |
| 12:51 | So in the command we can type xlim within brackets -1 comma 3 and ylim within brackets -15 comma 0. |
| 13:02 | This gives us the required rectangle. |
| 13:09 | This brings us to the end of this tutorial.In this tutorial,we have learnt to,Modify the attributes of plot like color, line width, line style by passing additional arguments. |
| 13:20 | Add title to a plot using 'title' command. |
| 13:24 | Incorporate LaTeX style formatting by adding a $ sign before and after the part of the string. |
| 13:30 | Label x and y axes using xlabel() and ylabel() commands. |
| 13:36 | Then, add annotations to a plot using annotate() command. |
| 13:38 | Get and set the limits of axes using xlim() and ylim() commands. |
| 13:46 | Here are some self assessment questions for you to solve. |
| 13:50 | 1. Draw a plot of cosine graph between -2pi to 2pi with line thickness 4. |
| 13:57 | 2. Read through the documentation and find out, is there a way to modify the alignment of text in the command ylabel. |
| 14:05 | Yes or No are the options. |
| 14:07 | And the final question. How do you set the title as x^2-5x+6 in LaTex style formatting.
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| 14:15 | Now, the answers, |
| 14:20 | 1. In order to plot a cosine graph between the points -2pi and 2pi with line thickness 3,we use the linspace and plot command as, x = linspace(-2*pi, 2*pi) |
| 14:41 | then plot(x, cos(x), linewidth=4) |
| 14:46 | And the second answer is No. We do not have an option to modify the alignment of text in the command ylabel. |
| 14:53 | Then the third and final one. To set the title in LaTex style formatting,we write the equation between two dollar signs as,
title("$x^2-5x+6$")
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| 15:11 | Hope you have enjoyed this tutorial and found it useful.
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Contributors and Content Editors
Gaurav, Kavita salve, Minal, PoojaMoolya, Sandhya.np14, Sneha
