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Hello Friends and Welcome to this tutorial on "Plotting Experimental data".

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At the end of this tutorial, you will be able to,

 Define a list of numbers.

 perform element wise squaring of the list.

 Plot data points.

 plot errorbars.

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One needs to be familiar with the concepts of plotting mathematical functions in Python.

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We will use data from a Simple Pendulum Experiment to illustrate.

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As we know for a simple pendulum, length L is directly proportional to the square of time T.

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We shall be plotting L and T square values.

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First we will have to initiate L and T values.

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We initiate them as sequence of values.

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We define a sequence by comma separated values inside two square brackets.

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This is also called a List.

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Let's create two sequences L and t.

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L = [0.1, 0.2, 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9]

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T= [0.69, 0.90, 1.19,1.30, 1.47, 1.58, 1.77, 1.83, 1.94]

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To obtain the square of sequence T we will use the function square with argument T.

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This is saved into the variable Tsquare.

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So type Tsquare=square withinbracket T

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Tsqaure enter

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Now to plot L versus T square, we will simply type

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plot within bracket L comma Tsquare comma within single quote dot

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Here single quote  dot displays the plot in a dot pattern.

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You can also specify 'o' for big dots.

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For this let us clear the first plot .

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Type clf closing  bracket and hit enter

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Then Type plot within bracket L comma Tsquare comma within single quote o hit  enter now  to clear the bracket type clf closing bracket

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Let us move further.

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For any experimental there is always an error in measurements due to instrumental and human constraints.

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Now we shall try and take these errors into account in our plots .

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Pause the video here, try out the following exercise and resume the video.

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Plot the given experimental data with large dots.

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The data is on your screen.

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Its given in delta underscore  delta L and delta underscore T

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We shall again initialize the sequence values in the same manner as we did for L and T.

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Now to plot L vs T square with an error bar we use the function errorbar() .

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Before plotting the data we need to get the data of delta L and delta  T

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delta  L= within square bracket 0.08,0.09,0.07,0.05,0.06,0.00,0.06,0.06,0.01

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delta  T= [0.04,0.08,0.03,0.05,0.03,0.03,0.04,0.07,0.08]

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Now use the error function

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Type errorbar within bracket L comma Tsquare comma xerr=delta underscore L comma yerr=delta underscore T comma fmt= in single quote bo

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This gives a plot with error bar of x and y axis.

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The dots are of blue color.

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The parameters xerr and yerr are error on x and y axis and fmt is the format of the plot.

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similarly we can draw the same error bar with small red dots just change the parameters of fmt to r dot.

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Type clf() to clear the plot
errorbar within bracket L comma Tsquare comma xerr=delta underscore L comma yerr=delta underscore T comma fmt=in single quote  r and hit enter.

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you can explore other options to errorbar using the documentation of errorbar.

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errorbar? on terminal

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Pause the video here, try out the following exercise and resume the video.

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Plot the given experimental data with small dots and also include the error in your plot.

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The data is on your screen for  delta s delta n

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This brings us to the end of the end of this tutorial.

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In this tutorial, we have learnt to,
1. to declare a sequence of numbers using the function array.

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2. to perform elementwise squaring using the square function.

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3. to use the various options available for plotting like dots,lines.

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4. to Plot experimental data such that we can also represent error by using the errorbar() function.

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Here are some self assessment questions for you to solve

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1. Square the following sequence.br distance underscore values=within square bracket 2.1 comma 4.6 comma 8.72 comma 9.03

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2. Plot L versus T in red pluses.

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And the answers,

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1. To square a sequence of values, we use the function square

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So that we have to Type square within bracket distance underscore values

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2. We pass an additional argument stating the desired parameter

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Type plot within bracket L comma T comma within single quote r+

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Hope you have enjoyed this tutorial and found it useful.

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Thank You!