MatLab

1
MatLab Palm Chapter 2, Part 3 Cell Arrays,
Structure Arrays

• Class 7.1
• Chapter 2 Sections 6 7

2
Announcements

• Departmental Presentations.(REQUIRED
  ACTIVITY)10/12 700-900 p.m. See online
  Schedule
• You must turn in two, one-page critiques (LIMIT
  EACH CRITIQUE TO ONE PAGE!), one for each
  presentation that you attend.
• Due Thursday, October 21, 2004.

3
Presentation Make-Up

• If you have a legitimate conflict
• Go to your conflicting class.
• Write a critique of the lecture/lab following the
  format below (two pages if course conflicts with
  both sessions of presentations) .
• On your cover sheet, give the course, section,
  and time of your conflict.
• Non-course-related conflicts REQUIRE instructor
  approval.

4
Critique format

• Introductory paragraph. Start with broad
  statement. Become more specific with sentences
  that define the engineering field you heard
  about. End with the topic sentence for your
  critique.

5
Critique format, continued.

• Example Introduction
• Civil engineers design, build and maintain
  our nations infrastructure. They take courses
  in structures, water resources, geotechnical
  engineering, construction management, and
  environmental engineering. These courses prepare
  them to work in large or small firms that are
  both governmental or private. Although there are
  specific areas that CE majors can focus in, many
  students choose the General Track, which
  requires them to take electives in each of the
  major areas within civil engineering. Because of
  its breadth, civil engineering is an interesting
  field, and the presenters for the department were
  very effective at communicating their enthusiasm
  for this subject.

Broad
Specific with definition
TopicSentence
6
Critique format, continued.

• Two to three supporting paragraphs. These
  paragraphs flesh out your topic sentence. They
  MUST contain
• A transition from the previous paragraph
• A key sentence (may be part of transition)
• Supporting sentences
• A concluding sentence

7
Critique format, continued.

• Example supporting paragraph
• Enthusiasm may be hard to define, but you
  know it when you see it. For instance, the
  geotechnical presenter had positive body language
  and used many personal examples to explain the
  topic. She talked clearly, in an animated voice,
  using a lot of hand gestures. She also had
  energy and showed by her facial expression that
  she was happy to be there and to have the
  opportunity to talk to our class. One example
  that stood out in my mind was how geotechnical
  engineers have to ensure that neighboring
  buildings are not damaged when a new facility is
  constructed. The picture of the subway pit right
  next to a major high-rise hotel brought that
  message home. Because of the active and
  interesting presentation style, this presentation
  kept my attention.

Transition
Key sentence
Supportingsentences
Conclusion
8
Critique format, continued.

• Conclusion paragraph. Should summarize the body
  of the critique and draw the important
  conclusions. Should NOT state substantially new
  material.

9
Critique format, continued.

• Example conclusion paragraph
• Through these many techniques, the Department of
  Civil Engineering made a strong presentation.
  Each presenter showed excitement, both through
  energy, inflection, and personal example, and
  through a communicated, genuine desire to inform
  us about their topic and to teach us. They were
  courteous in the way they treated late-comers and
  loud students, while not letting the presentation
  get out of control. They were also knowledgeable
  and able to answer questions. Hence, since this
  presentation was well-prepared and effectively
  delivered, I was encouraged that it was a
  beneficial use of my time.

Transition
Summary of supporting paragraphs
Final conclusion
10
Critique Style

• Each paragraph should be about the same length.
• Sentences should vary in length.

11
Critique Details

• Details (see example)
• 8 ½ x 11 paper, 1.5 times line spacing.
• One-inch margins on all sides.
• Times New Roman font.
• 12pt, bold title (maximum of two lines)
• 11pt body paragraphs.
• Underline Topic sentence, each key sentence,
  and your final conclusion sentence.
• Turn in three pages stapled(1) cover sheet with
  personal information, (2) critique 1, (3)
  critique 2.

12
Announcements, cont.

• Next Monday will be Case Studies, led by an
  industry sponsor (e.g. Dell, IBM, Frito Lay,
  Motorola, etc.)
• We may have handouts on Thursday, but make sure
  you arrive on time, and are courteous, attentive,
  and ready to work.

13
Team Exercise

• Budgetary estimateHow much will it cost each
  firm to give the case studies next week? Here is
  what we know
• Each team will be on campus for one full day.
• Each team is two to four people.
• Case studies require (?) hours of extra
  preparation by (?) numbers of workers.
• Travel is from within Texas.

14
Budgetary Estimate
These costs are paid by the companies as part of
their outreach/promotional budgets. This is
probably a LOW estimate.
15
Team Exercise (Adapted from Palm Ch. 3, No. 10,
p. 178)

• An object thrown vertically with a speed v0
  reaches a height h at time t where
• Write a function to compute h given v0 and t. It
  should allow t to be a vector.
• Use the function to PLOT (refer to p. 25) h
  versus t for t between 0 and 10 s and v0 50
  m/s.

16
Function file (velocity.m)

• function h velocity(v0, t)
• function h velocity(v0, t)
• This function computes the height h of an
  object at the time t after it is
• released. The initial speed of the object is
  v0.
• INPUTS
• v0 initial speed (m/s)
• t time after release (s)
• OUTPUTS
• h height (m)
• S. Socolofsky
• ENGR 111A 501-503
• October 12, 2004
• Define the acceleration of gravity
• g 9.81 m/s

17
Solution

• gtgt v_init 50
• gtgt t 00.110
• gtgt h velocity(v_init, t)
• gtgt plot(t, h)
• gtgt xlabel('Time after release (s)')
• gtgt ylabel('Height above release (m)')
• gtgt title('Position of a vertically released
  object')
• gtgt grid on

18
Lec. 7.1 Learning Objectives

• Understand the differences between vector,
  matrix, and structure arrays.
• Understand the definitions for structure, record,
  and field.
• Be able to create a structure array using at
  least two different methods.
• Be able to store, retrieve, and manipulate data
  in the different fields of a structure array.

19
Cell Arrays

• A Cell Array is an array where each index is also
  an array.
• Each index can be a different data type (i.e. you
  can have letters in one index and numbers in
  another).
• Allows you to give one name to a set of data that
  belong together.

20
Cell Arrays, continued.

• You can create Cell Arrays in two ways.
• Cell Indexing e.g. A(1,1) Walden
• Content Indexing e.g. A1,1 Walden
• Note the functions in Table 2.6-1 (p. 112)
• celldisp() and cellplot() are useful commands.

21
Cell Practice

• Type the following commands
• gtgt A 14, 0, 9, 2, 25, 68
• gtgt celldisp(A)
• gtgt cellplot(A)
• gtgt A1,3
• gtgt A(1,3)
• gtgt A(1,2)
• gtgt A1,2
• gtgt A1,2(1,2)
• gtgt A(1,2)(1,3) why it this an error?
• gtgt A1,2(1,3) why does this work?

22
New Topic Structure Arrays

• A structure array is a collection of records.
• A record is a set of related fields where each
  field may contain a different data type.
• A field is an array of data that defines a
  particular attribute of an object.
• structure array employee record
  employee(3) List of fields name, address,
  date of employment, salary.
• or
• The collection of fields comprise a record the
  collections of records comprise a structure array.

23
3.7 Structure Arrays

• Structure Arrays are like data objects in other
  languages.
• Structure(record).Field1 vector
• Structure(record).Field2 string
• Structure(record).Field3 number
• Fields can be arrays, character strings or
  numbers.

24
Structure Arrays

• By definition Structures are multidimensional
  MATLAB arrays with elements accessed by textual
  field designators.
• Examples
• Student.name Data Type Text
• Student(2).scores(3) Data Type Array of
  numbers.

25
Creating Structures

• Structures can be created dynamically by direct
  assignment to individual fields.
• array_name(index).field_name field_value
• An entire record (element of the array) can be
  added with a single statement.
• Clue(n) struct(field name 1,field-value-1,
  field name 2, field-value-2, .)
• When text values are entered for a field they
  must be enclose in single quotes.
• Note
• If there is only one record in a structure,
  there is no index needed between the array name
  and the field name. If more than one record
  exist then the index value must me given.

26
Sample of Direct Assignment

• Array names and fields can be created and
  assigned dynamically.
• Clue.who 'Prof Plum'
• Clue.where 'Study'
• Clue.what 'Candlestick'
• disp(Clue)
• who 'Prof Plum'
• where 'Study'
• what 'Candlestick'

27
More Samples

• Even though no index was used in creating the
• first record in 'Clue', another set can be
  appended
• by using an index.
• Clue(2).who 'Ms. Scarlet'
• Clue(2).where 'Library'
• Clue(2).what 'Rope'
• disp(Clue(2))
• who 'Ms. Scarlet'
• where 'Library'
• what 'Rope'

28
Adding Fields

• New fields can be added after structures
• have been created.
• Clue(2).turns 15 turns is a new field
• disp(Clue(2)) used 1st in record 2
• who 'Ms. Scarlet'
• where 'Library'
• what 'Rope'
• turns 15

29
Adding Fields

• Adding new fields will cause a 'null' field in
  the cells already defined.
• disp(Clue(1))
• who 'Prof Plum'
• where 'Study'
• what 'Candlestick'
• turns turns was not defined originally

30
The Array Function struct()

• All fields (a complete record) can be assigned
  with one statement. All text values are
  enclosed in quotes numerical data are not.
• Clue(3) struct('who', 'Col Mustard', 'where',
  'kitchen', 'what', 'revolver', 'turns', 22)
• disp(Clue(3))
• who 'Col Mustard'
• where 'kitchen'
• what 'revolver'
• turns 22

31
Using Array Functions

• What does this code segment do?
• Clue(1).turns 17
• avg_turnssum(Clue.turns)/length(Clue)
• disp(avg_turns)
• 18

32
Using Array Functions

• Since Clue(1).turns is null, , we can
  assign it a value.
• Clue(1).turns 17
• Below, notice the lack of an index for Clue and
  the square brackets around Clue.turn. This
  combination returns a vector of 'turns' to the
  MATLAB function, sum, which calculates the sum
  of that vector.
• The length function returns the number of
  records in Clue.
• Dividing the sum by the number of records gives
  us the average
• of the numbers stored in turns.
• avg_turns sum(Clue.turns)/length(Clue)
• Then we display our results, show 18 as the
  average.
• disp(avg_turns)
• 18

33
Try This!

• Use MATLAB to create a structure similar to the
  Clue Game Database in the examples.
• Try these commands in MATLAB
• Clue.who Clue
• Clue.who Clue(3).turns
• Clue.who Clue.where
• char(Clue.who) Clue(2).who
• Notice the different ways that the same data are
  presented.
• See a list of structure related function in Table
  2.7-1 on page 120 of the text.

34
RAT 7.1

• Take out a piece of paper, write your name,
  team, todays date and RAT 7.1.
• A structure array called profs has a field named
  college. How would you assign the value
  Engineering to this field for record number 2?
• You dont have to turn in your paper
• Answer gtgtprofs(2).college Engineering

35
Assignment 7.1

• INDIVIDUAL ASSIGNMENT
• Due March 9, 2004
• Chapter 2 49, 51 (End of chapter problems)
• Test your understanding problems 2.7-1,2,3 (p.
  123)