View source for Grace/C3/Data-Fitting/English-timed

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||'''Time'''
||'''Narration'''

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|| 00:01
|| Welcome to the tutorial on '''Data fitting''' in '''Grace'''.

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|| 00:06
|| In this tutorial, we will

Fit a given set of data points to a linear equation
 
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|| 00:14
|| Add two datasets to a graph panel
 
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|| 00:18
|| Add legends and format the legend properties

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|| 00:24
|| To record this tutorial, I am using

'''Ubuntu Linux''' 16.04 OS

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|| 00:33
|| '''Grace''' 5.1.25 and  '''Gedit''' 3.18.3

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|| 00:42
|| To follow this tutorial, 

Learner must be familiar with the '''Grace''' interface.

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|| 00:48
||  For pre-requisite tutorials, please visit this website.

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|| 00:54
||  Data fitting is a process to find a mathematical relation between two variables.

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|| 01:01
|| An equation is used to describe the XY dataset pair.

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||01:06
|| Using an iterative process, the coefficients are optimized.

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|| 01:11
|| The process returns the best possible coefficients for the equation.

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|| 01:17
|| Go to '''Desktop'''.  Notice the file, '''line-fit.txt'''.

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|| 01:24
|| This file is provided to you in the '''Code Files''' link. 

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|| 01:29
|| I have downloaded, extracted and saved the file to the '''Desktop''' directory.

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|| 01:36
|| Next, open the '''Grace''' program and load this file to plot an '''XY''' graph.

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|| 01:43
|| Choose '''XY''' data set, and '''autoscale''' data. 

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|| 01:48
|| Next I will format the plot.

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|| 01:52
|| I have changed the symbols, line style, tick marks and axis labels.

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|| 01:59
|| The data points do not lie on a straight line. 

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|| 02:04
|| The data points look scattered around a straight line.

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|| 02:08
|| We will fit this data to a straight line.

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|| 02:12
|| For a straight line, this is process is called '''linear regression'''.

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|| 02:18
|| A straight line is described by an equation in two variables,

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|| 02:24
|| The equation has the form, y equals mx+c.

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|| 02:29
|| Here, m is the slope of the line and c is the intercept. 

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|| 02:36
|| Go to '''Data''' and select '''Transformations'''.

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|| 02:42
|| Notice the available options.

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|| 02:46
|| Choose '''Regression''' from the list.

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|| 02:48
||A '''Regression''' dialog box opens.

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|| 02:52
|| Choose the data set of interest from '''Apply to set'''.

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|| 02:58
|| Currently only a single set is loaded and it is shown as '''S0'''.

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|| 03:05
|| The next number is the number of points that are present in the dataset.

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|| 03:12
|| If many datasets are loaded more sets will be seen, in the '''Apply to set''' box. 

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|| 03:19
|| Choose '''linear''' for '''Type of fit'''.

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|| 03:23
|| In the '''Load''' drop-down, choose '''Fitted values'''.

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|| 03:29
|| For '''restrictions''' choose '''None'''.

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|| 03:33
|| If only part of the data set needs to be fitted, enter the required range.

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|| 03:39
|| We can also specify the '''start load at''' and '''stop load at''' values in the form. 

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|| 03:47
|| I will leave it as is and will not make changes here.

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|| 03:52
|| Click on '''Accept''' to run the data fitting.

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|| 03:56
|| The data fitting algorithm runs.

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|| 03:59
|| A '''Grace console''' window appears with mathematical details.

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|| 04:04
|| We can see the equation used for the fitting.

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|| 04:08
|| The output values of residual, slope, intercept and other parameters are seen.

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|| 04:17
|| The fitted line appears on the screen.

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|| 04:21
|| The fitted values are loaded in a different set, '''S1'''.

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|| 04:26
|| Click on '''File''', '''Save''' to save the parameters.

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|| 04:31
|| The '''Grace: Save logs''' window opens.

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||04:35
|| In '''Save to file '''text box, type the filename as '''line-regression.txt'''.

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|| 04:43
|| Click on '''Apply''' and then click on '''Close''' to close the dialog box.

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|| 04:49
|| Close the '''Grace Console''' by '''File''', '''Close''' or press the'''Esc''' key.

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|| 04:56
|| Click on '''Close''' in the '''Regression''' window.

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|| 05:00
|| Double click on the line in the graph.

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|| 05:03
|| '''Grace Set appearance''' window opens.

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|| 05:07
|| In the '''select set''' form, select '''S1''' data set.

This is the fitted data.

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|| 05:15
|| Right click to open the context menu. 

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|| 05:19
|| Select '''Edit''', and in '''In spreadsheet''' option. 

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|| 05:24
|| The '''Grace: Spreadsheet dataset editor''' appears.

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|| 05:29
|| Notice the x and corresponding fitted y values of the fitted data.

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|| 05:36
|| These values are different from the input data.

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|| 05:40
|| This line fits the input data best, with a linear equation.

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|| 05:46
|| Close the '''Spreadsheet dataset Editor'''.

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|| 05:50
|| The original data set and the fitted values are the 2 datasets in the graph.

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|| 05:58
|| Datasets are labeled as ['''S0'''] for first set and ['''S1'''] for the second set.

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|| 06:05
|| We can add more datasets to this graph panel.

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|| 06:10
|| For this load the data using the '''Data, import, ASCII''' option from the menu.

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|| 06:18
|| Next, we will add legends to the plot.

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|| 06:22
|| Open the '''Set Appearance''' window and choose the dataset '''S0'''.

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|| 06:29
|| Under '''Legend''', in the '''String''' field, type '''Data''' as the legend label. 
Click on '''Apply'''.

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|| 06:38
|| Next choose '''S1''' dataset from the '''Select set''' data form.

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|| 06:45
|| Here, I will type '''Fitted data''' for the legend and click on '''Apply'''.

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|| 06:53
|| Close the '''Set Appearance''' window.

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|| 06:57
|| For some users, the '''legend''' position may be outside the graph border.

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|| 07:03
|| To reposition the '''legends''', place the cursor in the '''legend''' box.

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|| 07:09
|| Then press '''Control''' and '''L''' keys together.

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|| 07:13
|| The cursor changes to a pointer.

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|| 07:17
|| Left click and drag the '''legend''' box to the desired position.

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|| 07:24
|| Then, press '''Enter'''.

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|| 07:27
|| Press the '''Escape''' key to exit the movement mode.

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|| 07:32
|| Next, open the '''Graph appearance''' window.

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|| 07:36
|| In the window, click on the '''Legends''' tab, to format the '''legend''' fonts.

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|| 07:43
|| Under the '''text properties''', move the character size slider to 70.

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|| 07:49
|| The legends look very large compared to the graph.
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|| 07:53
|| I will retain the font type as '''Times-Roman'''.

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|| 07:58
|| Click on '''Apply''' to apply the changes.

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|| 08:02
|| Click on the '''legend box''' tab.

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|| 08:06
|| We can also specify the position of the '''legend''' in the location section.

I will leave it as is.

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|| 08:10
|| In the '''Frame line''' section, for '''Pattern''', I will choose '''None'''. 

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|| 08:22
|| Click on '''Apply'''.

This will remove the legend frame box.

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|| 08:28
|| Then '''Close''' the dialog box.

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|| 08:31
|| Now save the project in the '''Desktop''' directory.

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|| 08:36
|| I will use the file name '''regression dot agr'''.

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|| 08:41
|| Press '''Control Q''' or Click on '''File, Exit''' to exit '''Grace'''.

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|| 08:49
|| Let’s summarize.

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|| 08:51
|| In this tutorial we,

Performed data fitting for a straight line.

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|| 08:57
||Added two datasets in the graph panel.

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|| 09:01
||Added legends to the plot and  Formatted the legend properties.

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|| 09:08
|| For assignment activity, please do the following.
 
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|| 09:13
|| Two assignment files are provided in the Code files link.
 
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|| 09:18
|| Plot them in the same graph panel.

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|| 09:22
||  Perform quadratic regression on the '''parabola1.txt''' file.

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|| 09:28
||  Load the fitted data in the graph.
 
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|| 09:32
|| Add legend strings and reposition them inside the graph panel.

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|| 09:38
||  Format the appearance of the three datasets to distinguish them.

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|| 09:43
|| Your completed assignment may look similar to this.

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|| 09:48
|| This video summarizes the '''Spoken Tutorial Project'''.

Please download and watch it.

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|| 09:56
|| The '''Spoken Tutorial Project''' team:  conducts workshops and gives certificates.

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|| 10:03
||For more details, please write to us.

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|| 10:07
|| Please post your timed queries in this forum.

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|| 10:11
|| Spoken Tutorial Project is funded by '''NMEICT, MHRD''', Government of India.

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|| 10:19
|| More information on this mission is available at this link.

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|| 10:24
|| This is Rani from '''IIT Bombay'''. Thank you for joining.

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