9.7: Practice using a custom script
- Page ID
- 408552
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Install a custom script
The custom scripts (files with .m extension) and binary files (files with .mat extension) for this course are available here (click to go to OneDrive) using your Duke NetID. If you are using the Chemistry Department bohr server to access Matlab, the scripts are already installed for you.
If you are using your own computer, the scripts and binary files should be added to the correct folder on your computer. Follow the instructions in this video to install the lsq script, which performs least squares analysis.
Practice using a custom script and a binary file
This is an exercise to give you some practice in using Matlab to analyze data provided in a binary file, and plot the results using a custom script for least squares analysis. Before you start, make sure the custom files lsq.m and expt-1.mat are in your working MatLab directory (see video above). The binary file "expt-1" simply contains pre-defined 80 x 1 vector matrixes "x" and "y". This is just to save you the hassle of typing in the values for each vector.
One way to work through this activity is to open the "Practice_LiveScript_XXX.mlx" file, and simply follow the instructions within the Live Script document.
Follow the steps below (there is a video below to walk you through these steps):
- Open the MatLab program and be sure that you are working in the directory containing the lsq script and expt-1 binary file.
- Type the following: load expt-1
Your workspace now contains two variables, x and y which obey the following relation: \[y = Ae^{-Cx}\] - Plot y (ordinate) versus x (abscissa). Using Matlab, recalculate your data in linear form (ln y versus x) and plot the result. Using least squares analysis of the linearized data, calculate the values of A and C and report the standard deviation in these values. Using your calculated values of A and C, use Matlab to draw (a) the least-squares fitted line through your linear plot and (b) the best fit curve through your exponential plot. (NOTE: data should appear as points using the symbol 'o' and least squares fitted lines should be solid lines.)
Expectation for a full-credit plot:
- Data is plotted in scatter format.
- Axes are correctly labeled, with correct units.
- When appropriate, a curve fit to the data is shown
- equation of the line is shown on the plot, but not obscuring the data
- uncertainty in slope and intercept provided
- correlation coefficient (R) provided
- Approrpate units are given for every value and every axis label.
- Plot is centered on graph.
- Text is easily readable (usually this means it is large enough to read easily.
- You should show the plots described in (3) together with the values of A and C to your instructor. Each graph should have a title, and the x- and y-axes should be labeled.