Author: autarkaw

COVID19 Regression Model and Other Thoughts

March 28, 2020
I am not an epidemiologist but do regression modeling for a living. I have done regression modeling to predict student grades just after the first test, and now we will be using adaptive learning metrics to improve our identification schemes even earlier in the semester. It is not to spell boom or doom to a student but only to intervene early with personalized recommendations.
Looking at whatever data I can use and have time to scrape, four things are reasonably clear at this time to me about COVID19.
1) First, the rate of infection is exponential but it does not stay like that forever.  The logistic function of the infection rate is analogous to how the mass of a moving rocket decreases as it burns up its fuel. F=ma, but m is not a constant.
2) Second, President Trump is finally thinking about quarantining NY, NJ, CT area. A little late but it will definitely decrease the power of the exponent.
3) Third, we have to get more testing done but one which is totally random. We could have found the effect of the spring breakers coming to FL and of the college kids being sent home to parents who are having kids late in life. Please do not send your grandkids to grandpa/grandma’s retirement home. They may be the children of the corn.
4) Fourth, Florida and Louisiana need to get their head straightened out and use tougher rules to keep people inside and a method to keep outsiders out. They are the next hot zone.

How to Make a PDF file

Before COVID19 hit our lives, it was so easy for the student to submit a hard copy.  Now with soft copies being asked for, they and the instructors have to learn a bit.

So, I had this programming assignment before COVID19 closed our face-to-face classes. It involved handwritten pages, a published file, and writing out a short description of conclusions with equations in a word processor.  The student would print them all out at home or at the university, and collate them.  But now it has to be scanned and uploaded to the CANVAS learning management system.

So, if these three types of documents were to be uploaded as one pdf file, what would you do.  I am assuming that everyone has a smartphone (an iPhone or an android phone)

If you have a printer and a scanner

Print all the documents and scan the document as a pdf file

If you have a printer but no scanner

Print all the documents.  Download the CamScanner app on your iPhone or Android and follow the instructions of this YouTube video.

https://www.youtube.com/watch?v=UkYlGa3y4tk?start=0&end=196

Follow the directions up to the time it tells you how to email the document as I do not want you to email it to me.

If you have neither a printer nor a scanner

a) Take the handwritten documents. Download the CamScanner app on your iPhone or Android and follow the instructions of this

https://www.youtube.com/watch?v=UkYlGa3y4tk?start=0&end=196

Follow the directions up to the time it tells you how to email the document as I want you to upload it to CANVAS.

b) For typing the pages that include equations, use MS 365 Word, and develop your document.  Save it as a .docx file first, and only then save it as .pdf file.  You can save a document as a pdf file within MS 365 Word itself.

c) a MATLAB file can be published as a pdf file. See https://blog.autarkaw.com/2020/03/25/how-to-publish-in-matlab/

d) Merge pdf documents with Acrobat Pro. Did you know as a USF student you can download Adobe Acrobat for free?  It is a tool to make PDF files from wordprocessor docs as well as to merge them with other PDFs.  If you are a reader outside USF and do not have Acrobat Pro as it costs money, use https://smallpdf.com/merge-pdf. Just drag the pdf files, and it will merge them for you.

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The brute force way

(not recommended though but desperate times require desperate measures)

a) Take photos of each handwritten page.  Send the images to your email and save them on your computer.   Insert images (Insert -> Pictures in Word Menu) of the handwritten work into an MS 365 Word doc. But check your file size. It can get too big for CANVAS to handle and your internet to upload.  The limit may be 100MB.

b) For typing the pages that include equations, continue with the MS Word doc.

c) a MATLAB file can be published as a doc file. See https://blog.autarkaw.com/2020/03/25/how-to-publish-in-matlab/  Cut and paste it into the word doc.

d) Save it as a .docx file first, and only then save it as .pdf file.  You can save a document as a pdf file within MS 365 Word itself.

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How to PUBLISH in MATLAB

This is how you can get your mfile published.

Click anywhere in the mfile (if your cursor is not in the mfile, you may not get the proper menu open)

-> Go to PUBLISH
-> Click on Down Black Arrow under Publish
-> Choose Edit Publishing Option
-> click on Output file format and the right column entry will show html, but if you click on html, you will get a drop-down box as shown in the figure below.  Choose your option.

You can click on the figure below to see a larger version of the figure.

Watch the short video which illustrates the above.  Better to watch it in full screen.

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Ability to break long fprintf statements

Problem:
A student sent me an email – ” I can’t figure out how to continue my text on another line in the editor while using the fprintf command in MATLAB.  It seems like this should be something simple, but I can’t figure it out.  The closest thing I have tried is:
fprintf(‘filler filler filler’, …
‘filler filler’)

When I run this script, this only displays the content within the first set of quotes though.

Solution:
Assign the long strings to variables, and then use the fprintf statements

abc=’My name is’
def=’ Slim Shady, also known as Marshall Mathers’
fprintf([abc def])

or you could do the following, especially if you have other non-string variables to print

abc=’My name is’
def=’ Slim Shady, also known as Marshall Mathers’
fprintf(‘%s %s’,abc,def)

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On Making A Video Lecture on iPad and Uploading to YouTube

On Making A Video Lecture on iPad and Uploading to YouTube

Guest Blogger: Rasim Guldiken

Date: March 20, 2020

While we are scrambling to take the courses we teach from face-to-face format to remote format, we all could use simple tools to make the process simple and easy to implement.  I have created two extensive tutorials.

The first tutorial  shows step-by-step instructions on screencasting your lecture with an iPad using any stylus, editing the video in the Imovie app of iPad, uploading it to YouTube, or directly to your LMS.

[youtube https://www.youtube.com/watch?v=Nd3DqY6GsYE]

The second tutorial illustrates on how to embed any YouTube video to your Canvas LMS course content.

[youtube https://www.youtube.com/watch?v=Ji_a5BH0uvM]

I have been recording and uploading the videos to my Canvas course since Spring 2019, but following the same procedure has been frustrating as it takes several hours for videos to process. I really can’t blame anyone; there is an unprecedented load to the servers.

That is the reason I created this alternative method tutorial on using 1) YouTube as a platform to upload and store your content  and then 2) embedding the videos to Canvas.

This process works flawlessly as the videos are not stored on the LMS servers.

About the guest blogger

Dr. Rasim Guldiken is an Associate Professor of Mechanical Engineering at the University of South Florida.  His engineering education interests lie in open courseware for a course in Fluid Mechanics, metacognitive activities, and flipped learning.

Why Do We Use Numerical Methods?

Numerical methods are techniques to approximate mathematical procedures (an example of a mathematical procedure is an integral).

Approximations are needed because we either cannot solve the procedure analytically (an example is the standard normal cumulative distribution function)

or because the analytical method is intractable ( an example is solving a set of a thousand simultaneous linear equations for a thousand unknowns for finding forces in a truss)

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Why Don’t I Allow (Not Ban) Use of Cell Phones in Class – An Open Letter to Students?

Dear Students:

You are not allowed to use cell phones in this class — it is considered academic disruption. If you are expecting an important call or text, please let me know in advance and I will advise to sit at desks close to the door. You can quickly go outside to take the call or reply to your text. In a class of over a hundred, only a few people take me up on this offer, but the offer is available to you. “Loved ones though should call 911 in case of an emergency — the local responders will be there faster than you can.”

If you have an approved request for accommodation through the Student Disability Services to use your cell phone, please use it as per the allowed guidelines — just let me know in the first week of classes. You are being an exception to the policy is nobody’s business including mine. Do not be concerned about being “outed” — we all are outed every day – some are in a wheel chair while others use a skateboard, some can only take the elevator while others only take the stairs; some of us are not good looking while others are blessed with a head full of hair; some wear a head dress, while others have a skullcap on.

You are allowed to use flat laptops and tablets only if they are used to take notes with a stylus. A student cannot claim they want to type notes as that is virtually impossible to do in an engineering course lecture that is full of equations and sketches. Anyway, taking notes by hand is shown to be cognitively better than typing.

About those students who may mention personal responsibility and that disallowing the cell phone is an ego trip for me, how many studies do I need to show these students about negative effects of multitasking and working memory when one is learning something new.

The student use of cell phones distracts others and there are studies on that too.

Since we are using active learning in class, questions are encouraged even more so. It is harder to discern if a student is asking a question because of inattention or lack of understanding.  The former is a waste of precious class time for the rest of us.

And more importantly, removing temptation is much better than self-control. We only have so much self-control quota during the day – so having a no cell phone policy is helping the student to preserve some self-control for more important issues of the day.

Some may say, “Be more interesting than the incoming text”. I just cannot compete, as learning something new is hard and looking at a “Facebook like” is an immediate high.

Control the machine; do not let the machine control you.

Best of Learning
Autar Kaw
Your Instructor for Numerical Methods

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How do I solve simultaneous linear equations given in equation form? Updated Matlab 2018b

Guest co-blogger: : Luis Serrano

Many students ask me how do I do this or that in MATLAB.  So I thought why not have a small series of my next few blogs do that.  In this blog, I show you how to solve simultaneous linear equations given in equation form.

  • The MATLAB program link is here.
  • The HTML version of the MATLAB program is here.
  • DO NOT COPY AND PASTE THE PROGRAM BELOW BECAUSE THE SINGLE QUOTES DO NOT TRANSLATE TO THE CORRECT SINGLE QUOTES IN MATLAB EDITOR.  DOWNLOAD THE MATLAB PROGRAM INSTEAD

%% SUMMARY
% Language : Matlab 2018b;
% Authors : Autar Kaw and Luis Serrano;
% Mfile available at
% http://nm.mathforcollege.com/blog/SimultaneousEquationsEqForm.m;
% Last Revised : January 22, 2020;
% Abstract: This program shows you how to solve a set of
% simultaneous linear equations given in equation form?
% .
clc
clear all
%% INTRODUCTION
disp(‘ABSTRACT’)
disp(‘ This program shows you how to solve a’)
disp(‘ set of simultaneous linear equations given in equation form’)
disp(‘ ‘)
disp(‘AUTHOR’)
disp(‘ Autar Kaw and Luis Serrano’)
disp(‘ ‘)
disp(‘MFILE SOURCE’)
disp(‘ http://nm.mathforcollege.com/blog/SimultaneousEquationsEqForm.m’)
disp(‘ ‘)
disp(‘LAST REVISED’)
disp(‘ January 22, 2020’)
disp(‘ ‘)
%% INPUTS
% Enter the equations
syms a b c
eqn1=12*a+23*b+39*c==29
eqn2=13*a+17*b+19*c==37
eqn3=21*a+23*b+29*c==59
%% DISPLAYING INPUTS
disp(‘ ‘)
disp(‘INPUTS’)
disp(‘________________________’)
disp(‘Equations’)
disp(‘________________________’)
disp(eqn1)
disp(eqn2)
disp(eqn3)
%% THE CODE
% The solution
X=solve(eqn1,eqn2,eqn3);
% Assigning the output
a=double(X.a);
b=double(X.b);
c=double(X.c);
%% DISPLAYING OUTPUTS
disp(‘ ‘)
disp(‘OUTPUTS’)
disp(‘________________________’)
disp(‘Solution Vector’)
disp(‘________________________’)
fprintf(‘\nValue of a= %g’,a)
fprintf(‘\nValue of b= %g’,b)
fprintf(‘\nValue of c= %g’,c)
disp(‘ ‘)
disp(‘________________________’)

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How do I solve a nonlinear equation that needs to be setup – Updated to MATLAB 2018b

Guest co-blogger: Luis Serrano

Many students ask me how do I do this or that in MATLAB. So I thought why not have a small series of my next few blogs do that. In this blog, I show you how to solve a nonlinear equation that needs to be set up.

For example to find the depth ‘x’ to which a ball is floating in water is based on the following cubic equation
4*R^3*S=3*x^2*(R-x/3)
where
R= radius of ball
S= specific gravity of ball
So how do we set this up if S and R are input values?

The MATLAB program link is here.

The HTML version of the MATLAB program is here.

  • DO NOT COPY AND PASTE THE PROGRAM BELOW BECAUSE THE SINGLE QUOTES DO NOT TRANSLATE TO THE CORRECT SINGLE QUOTES IN MATLAB EDITOR.  DOWNLOAD THE MATLAB PROGRAM INSTEAD

%% SUMMARY
% Language : Matlab 2018b;
% Authors : Autar Kaw and Luis Serrano;
% Mfile available at
% http://nm.mathforcollege.com/blog/NonlinearEquations_withSetUp.m;
% Last Revised : January 22, 2020;
% Abstract: This program shows you how to solve a nonlinear equation
% that needs to set up as opposed that is just given to you.
clc
clear all
%% INTRODUCTION
disp(‘ABSTRACT’)
disp(‘ This program shows you how to solve’)
disp(‘ a nonlinear equation that needs to be setup’)
disp(‘ ‘)
disp(‘AUTHORS’)
disp(‘ Autar Kaw and Luis Serrano’)
disp(‘ ‘)
disp(‘MFILE SOURCE’)
disp(‘ http://nm.mathforcollege.com/blog/NonlinearEquations_withSetUp.m’)
disp(‘ ‘)
disp(‘LAST REVISED’)
disp(‘ January 22, 2020’)
disp(‘ ‘)
%% INPUTS
% Solve the nonlinear equation where you need to set up the equation
% For example to find the depth ‘x’ to which a ball is floating in water is based on the following
% cubic equation 4*R^3*S=3*x^2*(R-x/3) R= radius of ball S= specific gravity of ball So how do we set this up if S and R are input values
S=0.6
R=0.055
%% DISPLAYING INPUTS
disp(‘INPUTS’)
func=[‘ The equation to be solved is 4*R^3*S=3*x^2*(R-x/3)’];
disp(func)
disp(‘ ‘)
%% THE CODE
% Define x as a symbol
syms x
% Setting up the equation
C1=4*R^3*S
C2=3*x^2*(R-x/3)
f=C1==C2
% Finding the solution of the nonlinear equation
soln=vpasolve(f,x);
solnvalue=double(soln);
%% DISPLAYING OUTPUTS
disp(‘OUTPUTS’)
for i=1:1:length(solnvalue)
fprintf(‘\nThe solution# %g is %g’,i,solnvalue(i))
end
disp(‘ ‘)

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Solution to ordinary differential equations posed as definite integral

This blog is an example to show the use of second fundamental theorem of calculus in posing a definite integral as an ordinary differential equation.  This plays a prominent role in showing how we can use numerical methods of ordinary differential equations to conduct numerical integration.

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