diff -r 9bc78792904b -r 0ff3f1a97068 lstsq.rst --- a/lstsq.rst Fri Oct 08 11:31:56 2010 +0530 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,139 +0,0 @@ -.. Author : Nishanth - Internal Reviewer 1 : Puneeth - Internal Reviewer 2 : - External Reviewer : - -Hello friends and welcome to the tutorial on Least Square Fit - -{{{ Show the slide containing title }}} - -{{{ Show the slide containing the outline slide }}} - -In this tutorial, we shall look at generating the least square fit line for a -given set of points. - -First let us have a look at the problem. - -{{{ Show the slide containing problem statement. }}} - -We have an input file generated from a simple pendulum experiment. - -It contains two columns of data. The first column is the length of the -pendulum and the second is the corresponding time period of the pendulum. - -As we know, the square of time period of a pendulum is directly proportional to -its length, we shall plot l vs t^2 and verify this. - -#[Puneeth:] removed the explanation about loadtxt and unpack - option. It's been done in another LO already. simple dependency - should work? - -To read the input file and parse the data, we are going to use the -loadtxt function. Type -:: - - l, t = loadtxt("/home/fossee/pendulum.txt", unpack=True) - l - t - -We can see that l and t are two sequences containing length and time values -correspondingly. - -Let us first plot l vs t^2. Type -:: - - tsq = t * t - plot(l, tsq, 'bo') - -{{{ switch to the plot window }}} - -#[Puneeth:] Moved explanation of least square fit here. seems more -apt. - -We can see that there is a visible linear trend, but we do not get a -straight line connecting them. We shall, therefore, generate a least -square fit line. - -{{{ show the slide containing explanation on least square fit }}} - -As shown in the slide, we are first going to generate the two matrices -tsq and A. Then we are going to use the ``lstsq`` function to find the -values of m and c. - -let us now generate the A matrix with l values. -We shall first generate a 2 x 90 matrix with the first row as l values and the -second row as ones. Then take the transpose of it. Type -:: - - inter_mat = array((l, ones_like(l))) - inter_mat - -We see that we have intermediate matrix. Now we need the transpose. Type -:: - - A = inter_mat.T - A - -Now we have both the matrices A and tsq. We only need to use the ``lstsq`` -Type -:: - - result = lstsq(A, tsq) - -The result is a sequence of values. The first item in this sequence, -is the matrix p i.e., the values of m and c. Hence, -:: - - m, c = result[0] - m - c - -Now that we have m and c, we need to generate the fitted values of t^2. Type -:: - - tsq_fit = m * l + c - plot(l, tsq, 'bo') - plot(l, tsq_fit, 'r') - -We get the least square fit of l vs t^2 - -{{{ Pause here and try out the following exercises }}} - -%% 2 %% change the label on y-axis to "y" and save the lines of code - accordingly - -{{{ continue from paused state }}} - -{{{ Show summary slide }}} - -This brings us to the end of the tutorial. -we have learnt - - * how to generate a least square fit - -{{{ Show the "sponsored by FOSSEE" slide }}} - -#[Nishanth]: Will add this line after all of us fix on one. -This tutorial was created as a part of FOSSEE project, NME ICT, MHRD India - -Hope you have enjoyed and found it useful. -Thank you - -Questions -========= - - 1. What does ones_like([1, 2, 3]) produce - - a. array([1, 1, 1]) - #. [1, 1, 1] - #. [1.0, 1.0, 1.0] - #. Error - - 2. What does ones_like([1.2, 3, 4, 5]) produce - - a. [1.2, 3, 4, 5] - #. array([1.0, 1.0, 1.0, 1.0]) - #. array([1, 1, 1, 1]) - #. array([1.2, 3, 4, 5]) - - 3. What is the shape of the