Introduction To Matlab Class 2

1
Introduction To MatlabClass 2

• Instructors Hristiyan (Chris) Kourtev
• and Xiaotao Su, PhD
• Double click the matlab icon
• When prompted click Skip

2
Character Vectors And Numeric Vectors

• 'hello world' is referred to as a character
  string or a character vector
• 35, 26.3, 11, 4 is a numeric vector
• These are the two main data types in matlab

h e l l o w o r l d
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11)
35 26.3 11 4
(1) (2) (3) (4)
3
Character Vectors (aka Strings) And Numeric
Vectors

• How to convert between these two data types? What
  if I have a string, '39.5' and I want to add to
  it?
• num2str str2num
• str2num('39.5') 5
• 'hello w', 'orld'
• a 3, 9
• b 12.6, 8
• a, b
• c '1', num2str(39.5)
• str2num(c) 200

4
Formatting strings with sprintf

• result sprintf(format_string, input1, input2 )
• Format string flagswidth.precisionlength
  specifier
• Common Specifiersc characters
  stringd integere or E scientific
  notationf floating pointm 44.5 k hello
  worldres sprintf(s, it is d degrees
  outside, k, m)res will be hello world, it is
  44.5 degrees outside

5
Formatting strings with sprintf

• Flags- left justify default is right0 left
  pads the number with zeroes if padding specified
• Width just a number
• Precision just a number
• Examplessprintf('01.2f', 12.4) outputs
  12.40sprintf('010.2f', 12.4) outputs
  0000012.40sprintf('.3e', 362525200) outputs
  3.625e8
• For further reference go tohttp//php.net/manual
  /en/function.sprintf.php http//www.cplusplus.com
  /reference/clibrary/cstdio/sprintf/

6
Taking inputs

• Create a new program called math.m
• math.m
• Carries out a series of calculations on two
• numbers
• written by Your Name July 2010

7

• clear all
• take inputs
• num1input('what is the first number?')
• num2input('what is the second number?')
• show calculations
• disp(num2str(num1), '', num2str(num2), '',
  num2str(num1num2))
• disp(num2str(num1), '-', num2str(num2), '',
  num2str(num1-num2))

8
boolean expressions

• Boolean expressions either return 1 for true or
  0 for false
• Possible operators

gt gt lt lt
equals greater than greater than or equal to less than greater than or equal to and or
9

• 11
• (1 1)2
• (5 5) lt 10
• (5 5) lt10
• (1 1) (23)
• (1 1) (23)
• 5 (5 lt 10)

Note Put operations inside parenthesis so they
are preformed first.
10
Conditionals (if statements)

• if(Boolean Expression)
• do something
• end
• you can also do this
• if(boolean expression)
• do something
• else
• do something else
• end

or this if(boolean expression) do
something elseif(boolean expr2) do something
else end
11
Back to math.m

• if ( (round(num1)num1) (round(num2)num2) )
  
• disp('num1 and num2 are integers')
• end

12

• if ( (round(num1)num1) (round(num2)num2) )
  
• disp('num1 and num2 are integers')
• elseif(round(num1)num1)
• disp('only num1 is an integer')
• elseif(round(num2)num2)
• disp('only num2 is an integer')
• else
• disp('neither number is an integer')
• end

13
Task 1

• Have math.m tell me which number is larger then
  the other
• the biggest number is

gt gt lt lt
equals greater than greater than or equal to less than greater than or equal to and or
14
Tic and toc

• tic starts a timer
• toc tells you the number of seconds since when
  you ran toc

15
While loop

• while is a type of loop that runs while a
  condition is true
• while(boolean statement)
• do something many times
• end
• you would stop repeating the loop when the
• boolean statement is false OR if you use
• break

16
While program

• tic
• loops 0
• while(toclt5)
• loops loops1
• disp('number of loops ', num2str(loops))
• disp('number of seconds ', num2str(toc))
• end

17
While program stopping after 10 loops

• tic
• loops 0
• while(toclt5)
• loops loops1
• disp('number of loops ', num2str(loops))
• disp('number of seconds ', num2str(toc))
• if(loopsgt10)
• break
• end
• end