mat lab coding

MATLAB CodingCHEN 1703

My thanks to my colleagues for their contributions to this lecture:

Dr. James Sutherland, Dr. Leonard Pease, Dr. Michal Hradisky

ChEn 1703

Engineering ApproachFundamental

conservation lawsApproximations

& models

Algorithm (set of steps to

obtain an answer)

Solve by hand (pencil & paper,

calculator)

Solution

Numerical tools (help generate plots, calculate numbers)

MATLAB

Excel

Two engineering problems

What is the energy in/energy out ratio for in situ production of oil from shale?

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!!

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Data analysis - Using the right tool for the job



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250 m

450 m125 m



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!!

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Energy In (x10(kWh)

Oil Yield (m

Oil equivalent Energy Out (x10

NG equivalent Energy Out (x10

(kWh)

Case 1 13.9 592 6.33 6.84

Case 2 27.3 1,175 12.6 13.6

Case 3 43.2 1,120 12.0 12.9



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!!

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Energy In (x10

Oil Yield (m

Oil equivalent Energy Out (x10

NG equivalent Energy Out (x10

Energy In/Energy Out

Case 1 13.9 592 6.33 6.84 2.03 - 2.20

Case 2 27.3 1,175 12.6 13.6 2.00 - 2.17

Case 3 43.2 1,120 12.0 12.9 3.35 - 3.60


How does the NOx data from the simulation compare with the experimental data?

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How does the NOx data from the simulation compare with the experimental data?

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Port Location : 1

Probe Insertion Distance (" in from tile) Pressure Temperature O2 CO NO NO2 NOx

1 0.30 920 0.49 4470 9.4 0.0 9.44 0.40 930 0.44 4634 10.6 0.0 10.6 Temp = F7 0.70 930 0.40 4804 11.3 0.0 11.3 Dry, vol% O210 0.70 970 0.41 4671 11.0 0.0 11.0 `13 1.00 990 0.40 4628 11.5 0.0 11.5 (As corrected to 3% O2 by volume not done; numbers are raw)16 1.00 1040 0.42 4356 11.5 0.0 11.5 Number representspseudo-steady state reading after extracting for some period of time19 1.00 1070 0.39 4288 11.8 0.0 11.8 No replications22 1.20 1100 0.41 4547 11.7 0.0 11.7 Chevron ran @ fixed firing rate, not fixed steam quality25 1.20 1120 0.45 4586 11.4 0.0 11.428 1.40 1140 0.44 4505 11.1 0.0 11.131 1.40 1160 0.66 2929 9.7 0.0 9.734 1.30 1180 0.66 3039 9.5 0.0 9.537 1.20 1190 0.58 3993 11.4 0.0 11.440 1.20 1240 0.60 4561 11.3 0.5 11.843 1.20 1280 3.29 5000+ 6.1 1.5 7.646 1.20 1400 13.73 2864 2.2 2.8 5.049 0.5 1380 9.53 1320 2.0 5.8 7.852 0.7 1370 8.06 12 8.5 4.8 13.355 1.2 1780 7.95 7 8.3 4.5 12.858 1.3 1800 8.02 6 7.0 4.3 11.361 1.3 1835 8.16 5 5.6 3.8 9.4

62.5 (center of radiant section) 1.2 1855 8.25 4 4.7 3.5 8.2

Radiant Section Pressure Probe (Probe 1)

1 1/2 ft from burner endTime Stamp: 10:00 AM 2/20/07


How does the NOx data from simulation compare with experimental data? Solution = Extract data from simulation as f(location,time), write code to process data (spatial & time averages), make plots


Learning Objectives

Convert algorithm/flow charts into MATLAB code MATLAB Input/Output Logic (how we make decisions) IF/Case (the decisions) FOR and WHILE (the loops) Functions

Part 1: Input/Output

What are data input methods that you know?

• Command window

• Hard coding

• Ask for user input

What are data output methods that you know?

• No ;

• disp(x)

• fprintf

Basic MATLAB File I/O

save filename x y -ASCII • filename is the name of the file that you want to write data to.

• x, y are variables to be written to the file. ‣ If omitted, all variables are written.

• -ASCII tells Matlab to write the data in a format that you can read. ‣ If omitted, data will be written in binary format. ‣ best for large amounts of data

load filename x y • This is the complimentary command to save.

• Reads variables x and y from file filename ‣ If variables are omitted, all variables are loaded...

Saving variables to files & loading variables from files

clear;!x = linspace(-pi,pi);!y = cos(x);!save myVariables x y;! !clear;!load myVariables;!who; plot(x,y);

Formatted Output in Matlabdisp(x) - prints the contents of variable x. fprintf(...) - use for formatted printing • Allows much more control over output

• Syntax: fprintf(‘text & formatting’,variables); • Text formatting:

‣ %a.bc ‣ a - minimum width of output buffer

‣ b - number of digits past decimal point

‣ c - formatting scheme

‣ f - floating point (typical format) 12.345

‣ e - scientific notation - 1.2345e1

‣ s - string format

x = [1.1 2.2 3.3 4.4];!y = 2*x;!fprintf('Hello. (%1.3f,%1.3f), (%1.1f,%1.0f)\n',...! x(1),y(1),x(3),y(3));

Hello. (1.100,2.200), (3.3,7)

Control Code Description Example

\n Begin a new line fprintf('hello.\n');

\t Insert a “tab” fprintf('\thello.\n');

\\ insert a backslash fprintf('\\hello.\\\n');

'' Insert a single quote fprintf('''hello.''\n');

%% Insert a % sign fprintf(‘%%%1.2f\n’,95.6);

Formatted Output - Examples

fprintf('%6s%8s\n','index','value');!fprintf('--------------\n');! !n = 5;!a = zeros(5,1);!for( i=1:5 )! a(i) = 2*i+1;! fprintf('%6.0f%8.1f\n',i,a(i));!end

What does this output look like?

File Output in MATLAB

Three steps: • Open the file ‣ fid = fopen(filename,’w’);!

‣ ‘w’ tells matlab that we want to WRITE to the file.

‣ see “help fopen” for more information.

• Write to the file ‣ fprintf(fid,format,variables);

• Close the file

Example: Write code that produces a table of temperatures in F, R, C and K. User enters starting & ending temperatures (in F) & number of points in table. Write results to file called “tempTable.dat”

File Input in MATLABImport wizard “File→Import Data” • Allows you to import data from delimited files (spreadsheets, etc)

Importing “spreadsheet” data • dlmread - import data from a delimited file (you choose the delimiter) • xlsread - import data from Excel.

General file input - three steps: • fid=fopen(filename,’r’) - open a file to allow detailed input control. ‣ ‘r’ tells matlab that we want to READ from the file.

• a=fscanf(fid,format,size); ‣ Works like file writing, but use fscanf rather than fprintf. ‣ fid - file id that you want to read from ‣ format - how you want to save the information (string, number) ‣ ‘%s’ to read a string, ‘%f’ to read a floating point number, ‘%e’ to read scientific

notation. ‣ size - how many entries to read. ‣ feof(fid) - returns true if end of file, false otherwise.

• fclose(fid);

clear; clc;!!% open a file to read - first line contains!% the order of the polynomial. Second line!% contains the polynomial coefficients.!fid = fopen('poly.dat',’r’);! !% read the order of the polynomial!n = fscanf(fid,'%f',1);! !% read all of the polynomial coefficients!a = fscanf(fid,'%f',n+1);

4!1.0 2 0.02 4.0 0

2!0 1 2.3

“poly.dat”

“poly.dat”

File Input - Example

p(x) =4�

i=0

ai xi = a0 + a1x + a2x2 + a3x

3 + a4x4

p(x) =n�

i=0

ai xiGeneral form of an nth order polynomial:

For a quartic (n=4) we have:

Basic ConceptsPrograms

so farBranching

if(condition)

path if condition

is true

path if condition

is false

These basic elements can be combined to create complex program logic.

Looping

while( )!for( )

The “if” StatementBasic syntax: if ( condition1 )!% do some work!

elseif ( condition2 )!% do different work!

⋮!else!% do default work!

end

cond

ition

1

cond

ition

2

defa

ult

othe

r

cond

ition

s...

if ( condition )% do some work

end

if ( condition )% do some work

else% do default work

end

Create a MATLAB script to plot cos(x) an sin(x) on a user-specified interval. The user should be able to enter the interval in degrees or radians.

The “switch/case” StatementBasic syntax: switch switch_expression!! case case_expression!!! % do some work!

! case case_expression!!! % do different work!

⋮!! otherwise!!! % do default work!

end

case

1

case

2

defa

ult

othe

r

case

s...

Example - what is output? city=input(‘Enter the name of a city: ’,’s’)!switch city! case ‘Boston’!! disp(‘$345’)! case ‘Denver’!! disp(‘$150’)! case ‘London’!! disp(‘Arm and Leg’)! otherwise!! disp(‘Airfare not on file’)!end

Relational OperatorsTrue condition represented by a nonzero (typically “1”). False condition represented by zero “0” Can be applied to scalars, vectors, or matrices.

Statement Result Example True or False

a == b true if a and b are equal 5==3 0

a ~= b true if a and b are NOT equal 5~=3 1

a < b true if a is less than b 5<3 0

a > b true if a is greater than b 5>3 1

a >= b true if a is not less than b 5>=3 1

a <= b true if a is not greater than b 5<=3 0

Comparison Operators

Example: What does this do?dice = 3*rand(1); % a number between 0 and 3!if( dice<1 )! name = 'Bob';!elseif (dice<2)! name = 'Fred';!else! name = 'Jane';!end! !dice = 3*rand(1); % a number between 0 and 3!if dice<1! age = 25;!elseif dice<2! age=19;!else! age = 40;!end! !fprintf('\n%s is %1.0f years old\n\n',name,age);

NOx Data Analysis

NOx Data Analysis if axial_loc == 1: axial_name = '0_457m' dataFile = 'chevron_expData/chevron_1.5ft.dat' dist = '1.5_ft' elif axial_loc == 2: axial_name = '1_372m' dataFile = 'chevron_expData/chevron_4.5ft.dat' dist = '4.5_ft' elif axial_loc == 3: axial_name = '2_287m' dataFile = 'chevron_expData/chevron_7.5ft.dat' dist = '7.5_ft' else:

print('You selected an invalid option for axial location')

NOx Data Analysis Extracted data from simulation is saved in directories with the following names: 0_457m, 1_372m, 2_287m.

Write a script that uses an if/elseif structure to determine which directory to process

Now do the same thing using a switch/case structure

See http://blogs.mathworks.com/pick/2008/01/02/matlab-basics-switch-case-vs-if-elseif/

http://blogs.mathworks.com/pick/2008/01/02/matlab-basics-switch-case-vs-if-elseif/

Relational OperatorsTrue condition represented by a nonzero (typically “1”). False condition represented by zero “0” Can be applied to scalars, vectors, or matrices.

Operator Description

& Element-wise AND - returns an array of 1 and 0.

| Element-wise OR - returns an array of 1 and 0

~ Element-wise NOT - returns an array of 1 and 0

Logical Operators

Function Description

any(var) returns true if any element of var is true

all(var) returns true (1) if all elements of var are true.

find(var) returns the indices where var is true (nonzero).

isequal(var1, var2) returns true (1) if the two arrays are equal.

strcmp(str1,str2) Compares two strings and returns true if they are equal.

abs(var) returns the absolute value of all elements of var.

ceil(var) rounds all elements of var up.

floor(var) rounds all elements of var down.

mod(var1,var2) Remainder of division of var1 by var2.

A Few More Useful Functions

Example - Data Analysis

Generate a set of random numbers between 1 and 100.

• What percentage of these numbers are between 40 and 60?

• How many numbers did it take to get a consistent answer?

Repeat this example to determine what percentage are between 90 and 95.

Hint: use rand & find functions.

The “for” StatementPredetermined looping

Basic syntax:

for(counter=start:step:stop)% do some work

end

increment counterby step each timeloop is executed.

Example - what are the values in a? n=10;!a = zeros(n,1);!for i=1:1:n! a(i) = 2*i;!end


Basic syntax:


end



Example - what are the values in a? n=10;!a = zeros(n,1);!for i=1:n! a(i) = 2*i;!end


Basic syntax:


end




Example - what are the values in a? n=10;!a = zeros(n,1);!for i=n:-1:1! a(i) = 2*i;!end


Basic syntax:


end




Example - what are the values in a? n=10;!a = zeros(n,1);!for i=n:-1:1! a(i) = 2*i;!end

Example - what are the values in a?!a = zeros(3,1);!for i= [1 2 5]! a(i) = 2*i;!end

The “while” StatementConditional Looping

Basic syntax:

while ( condition )% do some work - must result% in condition being changed% at some point!

end

Example - What is the value of n? a = 1;!n = 0;!while (a<10)! a = a+2;! n = n+1;!end

check conditioneach time loop is

executed.

How “while” can trip you upMost important thing about WHILE is missing from this loop; what is it?

Exit criteria is never reached because value of condition variable stops changingWhat can you do?

Ctrl+C to break the loop manuallyUse break - Statements in loop after break do not execute. If loops are nested, control

passes to statement that follows end of loop.Assign variable that acts as counter, break if counter gets too high

Example - What happens here? n = 0;!k = 1;!while n < 2! n = n + 1/k;! k = k*2;!end!n!k

How “while” can trip you upMost important thing about WHILE is missing from this loop; what is it?

Exit criteria is never reached because value of condition variable stops changingWhat can you do?

Ctrl+C to break the loop manuallyUse break - Statements in loop after break do not execute. If loops are nested, control

passes to statement that follows end of loop.Assign variable that acts as counter, break if counter gets too high

Example - What happens here? n = 0;!k = 1;!while n < 2! n = n + 1/k;! k = k*2;!end!n!k

Example - What happens here? n = 0; k = 1; count = 0; while n < 2 n = n + 1/k; k = k*2; count = count + 1; if count > 100 break end end n k count

The “break” Statement“break” exits the current loop structure.

What control structure would produce these two pictures?

condition is satisfied

Example - Compute polynomial

p(x) =4�

i=0

ai xi = a0 + a1x + a2x2 + a3x

3 + a4x4

p(x) =n�

i=0



Read coefficient values from file, compute f(x)

Example - Compute polynomial

p(x) =4�

i=0

ai xi = a0 + a1x + a2x2 + a3x

3 + a4x4

p(x) =n�

i=0



Read coefficient values from file, compute f(x)clear; clc;!!% open a file to read - first line contains!% the order of the polynomial. Second line!% contains the polynomial coefficients.!fid = fopen('poly.dat',’r’);! !% read the order of the polynomial!n = fscanf(fid,'%f',1);! !% read all of the polynomial coefficients!a = fscanf(fid,’%f',n+1);!!% add in loop to read multiple sets of coefficients from poly.dat, compute f(x) for all sets of coefficients

Example: Factorial

Write a Matlab code to calculate the factorial of a number using:

1. A for loop 2. A while loop

n! =n�

i=1

i

NOTE: MATLAB’s factorial function will do this much faster than using loops will.

mat lab coding

Documents

data analysis

nox data

experimental data

extract data

right tool

jobtwo engineering problemshow

x10ng equivalent energy

situ production of oil