IT1005

1
IT1005

• Lab session on week 7 (3rd meeting)
• Welcome back from Mid semester break )
• (a. k. a Mid test period)

2
Remember This (Again)!

• E-mail your answers (in Microsoft Word format)
  tostevenhalim at gmail.com
• With EMAIL subject
• IT1005-LabGroupID FullName,
• e.g. IT1005-7A StevenHalim
• Mr Gmail will sort your emails for me )
• Wrong subject header will confuse Mr Gmail
• Try to submit your answers ONCE before deadline!
• Do not submit again to fix some minor mistakes or
  to reconfirm!
• Shorter (but correct) answers better marks )
• Remember, I have 90 emails/week !

3
Violations ?

• There are several violations for lab 3
• Mostly by those who do not actually attend my
  classes
• I have decided that there is no penalty for lab
  3
• Only late submission get -1 mark (per day)
  penalty.
• For lab 4 onwards, no more mercy
• Every violation for this e-mail submission
  mechanismwill result in deduction of 1 mark from
  the offenders marksfor that particular lab.

4
Lab 3 Answers (1)

• Q1 Operations on Matrix
• Results
• 33 matrix ? create array ? change row
• 024 ? start from 0, increment by 2, stop until
  4, etc.
• Several options
• Manual, not advisable, B 0 2pi 4pi or
  B 0 2 4 pi
• Semi manual, B 02pi4pi or B 024
  pi
• Assuming A exist B Api or B A.pi (.
  is actually not needed as pi is scalar).
• Several options, if I am the lecturer, I will ask
  you to list at least 4 ways!
• Wrong, C 16pi 14pi 12pi , not using
  matrix B as reference!
• Manual, not advisable, C B(3,3) B(3,2) B(3,1)
  .
• Use loop/index, C B(3-11,3-11) C
  B(end-11, end-11) or C B(3 2 1,3 2 1)
• Use Math, C 16pi - B or C repmat(16pi, 3,
  3) - B
• Use sort, C sort(sort(B,1,'descend'),2,'descend'
  )
• Use rotate, C rot90(B,2) or C
  rot90(rot90(B))
• Use flipup and fliplr, C fliplr(flipup(B))

5
Lab 3 Answers (2)

• Q2 Operations on Matrix
• D A()
• D is a 91 column vector.
• Listed column by column or according to the
  indexes of each element.
• Please specify the order! Otherwise I can say
  zig-zag/random/row by row patterns!
• A(1,) repmat(-2,1,3)
• There are several ways to execute this repmat
  function!
• A(1,) repmat(-2,1,1) also works Why?
• A(1,) -2 also works Why? (but this one is
  wrong since it does not use repmat).
• A(,2) zeros(3,1) pi
• There are several ways to write the zeros
  function. Actually zeros is redundant here!
• A(,2) zeros(1,3) pi also works Why?
• A(,2) zeros pi also works Why?
• A(,2) pi also works Why? (but this one is
  wrong since it does not use zeros).
• 2B 2C scalar expansion is ok, but to avoid
  confusion, lets try to be precise!

6
Lab 3 Answers (3)

• Q3 Plotting multiple graphs on the same figure
• Observed
• Two graphs on one figure.
• We can do the same thing with hold on! I have
  shown it 2 weeks ago (creating flatland).
• Say that y is sine graph, z is cosine graph
  within domain -2pi to 2pi, range -1 to 1.
• The color of the graphs are blue and green
  because of Matlab settings.
• You can actually specify plot colors!
  plot(x,y,r,x,z,m) r - red, m - magenta.
  Try!
• Several options
• Bad, create E from scratch.
• Assume B exists, then create E from B by dividing
  B with ./ 1 2 3 4 5 6 7 8 9.
• Apply F sin(E) ? element by element.
• Several options
• plot(E(,1),F(,1), E(,2),F(,2),
  E(,3),F(,3)) grid
• plot(E,F) grid ? This also works because Matlab
  access matrix column by column.
• We observe three not so precise sine graphs on
  one figure.
• No relational or logical questions actually
  These are for lab 4

7
Midterm test answers

• Only if at least 5 students want to know the
  truth ?
• B. 3.0 GHZ, 1 GB DDR-RAM is still faster than 3.2
  GHZ, 1 GB DRAM.
• D. 0/1 only.
• B. x1, y0, z1.
• E. None of the above. B, C, D are definitely
  wrong (not binary), A is also wrong because 63
  is one less from 64 (exact multiple of 2),
  thus it will not have 0 just before the
  fraction point.
• B. Step refinement. Coarse, fine grained, etc.
• D. Little_three_cats are the only valid
  variable,try isvarname(Little_three_cats).
• B. x is 20. both long variable name 63 chars
  will be truncated into max 63 chars, thus both
  looks the same for Matlab. Thus x 10 10.
• D. SimpleSimon3 ? is comment, so this is
  basically print out the current value of
  SimpleSimon (assumed to be a valid variable, as
  stated in the problem description).

8
Midterm test answers

• Only if at least 5 students want to know the
  truth ?
• A. x is 3.8278, apply the BODMAS! Just be careful
  with \ (reverse operand)
• B. A will contain values between 31 and 61
  inclusive, in increments of 2. This is due to
  scalar expansion.
• E. None of the above. A and B are not scalar,
  thus no scalar expansion.The . is element by
  element multiplication? matrix dimension must
  agree.
• D. C is a 3x3 matrix containing pi in all
  elements except the diagonal (2pi).eye ?
  identity matrix 1 0 0 0 1 0 0 0 1!
• A. C contains the value 1.A(2-11, 23) will
  produce 5 6 3 4Searching for 5 in the linear
  version of A 5 3 6 4 returns index 1.
• D. A 1 3 5 2 4 6 1 2 2 Similar as our lab
  3.
• D. X 2. Just simulate the process.
• E. Colin Tan and Saif Khan. Too bad if you get
  this wrong p.

9
What we have learned so far

• Top Down Design to create programs
• Big steps, small steps, comments, Matlab codes.
• Matlab program itself
• Command/figure window, workspace, debugger, etc.
• Things about Matlab array/matrix
• Creation, Deletion, Access, Update, Operations,
  etc.
• Math and logic operations
• BODMAS, Relational (, , Or, Not).
• Is it enough to create more complex programs?
• So far our programs are straight from start to
  end.
• Single sequence

10
Review on Control Structures

• Sequence
• Superman example (wrong sequence of something
  important)
• How to exit from this room?
• Repetition
• for-end ? if your repetition related to
  counting
• while-end ? if you need to repeat until some
  event occurs
• e.g. Count sum of square numbers from 1 up to n2
  149n2 ?
• Selection
• if-end ? only test one condition
• if-else-end ? one condition versus the rest
• if-elseif-else-end ? several conditions
• switch ? several equality conditions, not ok for
  INEQUALITIES!

11
Quick Test on Control Structures

• Decide what to do if an earthquake happens HERE
  and NOW!
• Simulate an ATM machine that can do these simple
  operations
• Dispense money
• Check PIN
• Ask amount to be withdrawn
• Deduct the users account
• Ask for ATM card
• ??? err something fishy ???

12
Lab 4 Free and Easy Time

• Now, you are free to explore Matlab,especially
  to find answers for Lab 4.
• For those who have done Lab 4, try this extra
  challenge!The solution is at the end of this
  session
• Lets create our own ATM machine ?.
• Operations as listed previously (now in logical
  order)
• Ask for card
• Check PIN
• Ask amount to be withdrawn
• Dispense that money
• Deduct the users account