Engr/Math/Physics 25
Chp3 MATLAB
Functions: Part4
Bruce Mayer, PE
Licensed Electrical & Mechanical Engineer
BMayer@ChabotCollege.edu
Engineering/Math/Physics 25: Computational Methods
1
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Learning Goals
 Understand the difference Built-In and
User-Defined MATLAB Functions
 Write User Defined Functions
 Describe Global and Local Variables
 When to use SUBfunctions as
opposed to NESTED-Functions
 Import Data from an External Data-File
• As generated, for example, by an
Electronic Data-Acquisition System
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Private Functions
 Private functions reside in subdirectories
with the special name private, and they are
visible only to fcns in the parent directory
 Assume the directory wmays is on the
MATLAB search path. A subdirectory of
wmays called private may contain functions
that only the functions in wmays can call.
 Because private functions are invisible outside
the parent directory wmays, they can use the
same names as functions in other directories.
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Data Acquisition
 At Some Point in His/Her Career Virtually
EVERY Engineer will need to ACQUIRE and
ANALYZE data from some PHYSICAL system
 The Acquisition of large amounts of Digital
Data used to be quite difficult, but today
modern Electronics makes this MUCH easier.
 Main Steps in the design of a Data Acq Sys
• Determine WHAT Data to Collect (can be HARD)
• Obtain electronic measurement SENSORS
• Obtain Sensor↔Computer INTERFACE Hardware
& Software to collect data in digital form
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Typical Data Acq Sys.
 Items  &  → Sensor;
Sensor: Power &
Signal-Conditioning
Engineering/Math/Physics 25: Computational Methods
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 Item  → USB or Serial
Connection
 Item  → Interface
Software Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Design: Data-inputs, Sensors
Qty
Description/Location
Type
Pwr Src
02
Immersed in coolant
stream at Supply & Return
connections of chiller
Temp
K TC
n/a
[Strawberry Tree Data
Acq] [laptop]
Need to install 3/8-Tu to 1/4FPT branch TEE in chiller
plumbing to add 083886 &
080144. TEE = SS-600-3TTF
13
Temp array around the
new TMB bubbler
Temp
K TC
n/a
[Strawberry Tree Data
Acq] [laptop]
Order 2nd DATA shuttle. See
item 4932. See bubtcloc.dwg,
or prs39602
03
Collant flow leading into
the three bubblers
Fluid Flw
Turbine
meter
12 Vdc from NOSHOK controllers
[modifed 973680 V-divider
card] [Strawberry Tree
Data Acq] [laptop]
3 wires: +12Vdc from
NoShok, com from NoShok,
sq-wave pulse to NoShok
03
MFM on output of bubblers
to measure the Qv,B+QN2
mixture output of bubblers
0-5 Vdc
Output 
flow
WJ-1000 system
[Strawberry Tree Data
Acq] [laptop]
Use Tylan MFC/MFM
extension cards, pn 3780-280
02
In & Out signal on ch2&3
TMB bubbler Hi-res card
channel. Card = 80 CARD.
Vin = TP8, Vout = TP16
0-5 Vdc
Output 
-30 °C
+70 °C
WJ-1000 system
[TP8 & TP16] [Strawberry
Tree Data Acq] [laptop]
See item 5270 for Strawberry
Tree over-voltage calcs OK
Use Tylan MFC/MFM
extension cards, pn 3780-280
01
Absolute Barometric
Pressure. Locate Setra270 sensor on top of
system
0-5 Vdc
Output 
800 1100
mBar PA
24Vdc, bench top
pwr supply from
FPD handler project
[Strawberry Tree Data
Acq] [laptop]
Bench test req’d for
"088603-000 xdcr,press,0100 psig,atm (model 270)"
24 V pwr supply also power
the NoShok controllers
Engineering/Math/Physics 25: Computational Methods
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Output To
Notes & Comments
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Sensor Placement Design
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Computer DataAcq DataFlow
Board 1:1194
Write 1194a
Bub TCs
0-5V -> Torr
Atm Press
Computer Interface Cards
Ch2 &3 Tsens
Write1194b
Ch2&3 Thires
Board 2:1159
Write 1159a
Write1159b
TEOS Line TC
Chiller TCs
Board 3: 160
Write 160a
“soft” Charts
Bub N2 MFCs
MFMs
TP1: V -> C
Ch2&3 Bub T
Write160b
TP9: V->C
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Data Files
 Most DataAcq Systems record the data using
characters listed in the American Standard
Code for Information Interchange (ASCII)
• The Base ASCII set contains 128 characters (hex 7F)
• The Extended set contains 256 characters (hex FF)
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Data Files cont
 Data Files Usually have File Extensions
of .dat or .txt
• Many others exist
– in Feb10 found 3737 Different Data Files types on
http://www.webopedia.com/quick_ref/fileextensionsfull.asp
 Windows Wordpad.exe creates ASCII text, and
is typically used to EDIT Data Files
• Or in MSWord you can save/read files as ‘text only’
– Change the DataFile extension to “.txt” if needed
 Many Times Data Files Have “Headers” that
need to be stripped OUT to Expose data-only
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Data File Examples
 KLA-T “KLARFF file fragment
DEFECTID XREL YREL XINDEX YINDEX XSIZE YSIZE DEFECTAREA DSIZE CLASSNUMBER TEST IMAGECOUNT ;
DefectList
1 2.7076600000e+02 3.6191450000e+03 -4 1 0.249000 0.249000 0.032000 1.7800000000e-01 0 1 0
2 1.5445400000e+02 2.5059200000e+03 -4 -2 0.249000 0.249000 0.027500 1.6500000000e-01 0 1 0
3 1.8203200000e+02 2.3367030000e+03 -4 -3 0.499000 0.499000 0.046800 2.1600000000e-01 0 1 0
4 3.8058700000e+02 2.0016480000e+03 -4 -3 0.249000 0.998000 0.046800 2.1600000000e-01 0 1 0
5 9.2548000000e+01 4.8907490000e+03 -4 -4 0.249000 0.249000 0.032000 1.7800000000e-01 0 1 0
• SPACES Separate the Data FIELDS
 StrawBerry Tree DasyLab-Software file
WorkBench PC for Windows - V 2.60.00
WORKSHEET
: 960411D3
Recording Date
: 4/11/96, 15:28:28
Block Length
: 8
Delta
: 0.500000 sec.
Number of Channels : 4
Date;Time;TC14: TEOS Line (C);TC16: TEOS Line (C);TC17: Chllr Sup (C);TC18: Chllr Ret
(C);
4/11/96;15:28:28.0;74.908;86.706;-22.458;-19.720;
4/11/96;15:28:28.5;74.938;86.716;-22.467;-19.716;
4/11/96;15:28:29.0;74.952;86.705;-22.499;-19.706;
4/11/96;15:28:29.5;74.980;86.702;-22.509;-19.695;
• SEMICOLONS Separate
the Data FIELDS
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Data File Examples
 FLUKE ScopeMeter .csv Data File Fragment
","Input A",
",1,
","Envelope",
",13/32/94,
",19:34:51,
",5.0E-03,
",-1.00E-02,
",2.500000E+01,
",254,
","s",
","5 ms/Div",
",2.00E+00,
",6.32E+00,
",2.500000E+01,
",256,
","V",
","V",
-1.00E-02,5.6E-01,6.4E-01
-9.8E-03,4.0E-01,5.6E-01
-9.6E-03,4.8E-01,5.6E-01
-9.4E-03,4.0E-01,5.6E-01
-9.2E-03,4.0E-01,5.6E-01
-9.0E-03,4.0E-01,5.6E-01
Test-Point-3 SCOPEMETER DEMO BOARD 4022 245 0422.2
9.0
Signal (Vdc)
8.0
7.0
ScopeMeter Signal (Vdc)
"Title
"ID
"Type
"Date
"Time
"X Scale
"X At 0%
"X Resolution
"X Size
"X Unit
"X Label
"Y Scale
"Y At 50%
"Y Resolution
"Y Size
"Y Unit
"Y Label
6.0
5.0
4.0
3.0
2.0
1.0
0.0
-0.01
0.01
0.02
0.03
Time (s).
0.04
file = SM_Demo_Board_0210.xls
DataFile HEADER
COMMAS Separate Data
Engineering/Math/Physics 25: Computational Methods
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0.00
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Import Data into MATLAB

Once the DataAcq System Generates reams
of Digital Data, the Engineer or Scientist
needs to ANALYZE it To discern its
MEANING

MATLAB has Extremely Powerful
Data-Analysis Tools, but we need to get the
data INTO MATLAB first

MATLAB provides a Windows-type “wizard”
to IMPORT the data; bringing data-file values
into the MATLAB Environment
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
MATLAB: Data Import/Analysis

Recall the Fluke ScopeMeter .csv file

We Want to import the Data from This File
and plot it it Using MATLAB
Cables To/From
AcceleroMeter
Omega ACC-PS1
AcceleroMeter
Power Supply
ScopeMeter used
for Voltage-Level
Data Acquisition
Fluke-199 200 MHz
ScopeMeter
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Data Acq from H2 Fuel Cell
MotorCycle (H2 @ 5000 psig)
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
All Done for Today
Fluke
ScopeMeter
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Engr/Math/Physics 25
Appendix
f x   2 x  7 x  9 x  6
3
2
Bruce Mayer, PE
Licensed Electrical & Mechanical Engineer
BMayer@ChabotCollege.edu
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Import ScopeMeter .csv Data
 Start the Import
Wizard
 Locate Directory
with DataFile
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Import TP3 .csv Data
 Find and OPEN DataFile
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Import TP3 .csv Data
 MATLAB AutoMatically picks Comma for
“Select Column Separator(s)”
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Import TP3 .csv Data
 BUT, Data does NOT Preview Properly
 Suspect HEADER as cause
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Import TP3 .csv Data
 Edit Header with
MS WordPad
HEADER
contains
NUMBERS –
Suspect this is
the problem
Replace with
Pure TEXT
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Import TP3 .csv Data
 Give File NEW name
to preserve original
Form of Data
 Replace Header w/ 3
lines of Text
• All No.s Preceded by
Letter(s)
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Import TP3 .csv Data
 Use Import Wizard to
Open NEW .csv file
 Preview Looks
MUCH better
• Even Picked Out
Column Headers
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Import TP3 .csv Data
 The DATA Preview Looks Really Promising
 Data Values Arrayed in SpreadSheet-like
cell arrangement → click Next>
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Import TP3 .csv Data
 Can Chose Variable Format as either:
3-Col ARRAY or 3 individual Col-VECTORS
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Import TP3 .csv Data
 Do it the HARD way with 3-Col Array
• Change VAR name to meaningful Value
 MATLAB Array Var named SM_TP3 → click
Next>
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Import TP3 .csv Data
 Chk that SM_TP3
appears in
WorkSpace
• SoFar, SoGood...
 Now Some Physics
• At each Sample
Time the ScopeMeter
Records TWO Data
Points during the sampling interval: Max & Min
 Choose to Plot MAX, which is stored Col-3
• c.f. Column-3 on previous slide
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Plot TP3 t vs V Data
 The Command Window Plotting Session
>> % make time vector, t, from Array Col-1
>> t = SM_TP3(:,1);
>> % construct voltage vector, V, from
Array Col-3
>> V = SM_TP3(:,3);
>> plot(t,V), xlabel('Time (s)'),
ylabel('TP3 E-Potential (volt)'),...
title('Fluke ScopeMeter SignGen TestPt3'), grid
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Plot TP3 t vs V
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Nested Functions
 MATLAB permits
placement of the
definitions of one or
more functions within
another function.
Functions so defined
are said to be nested
within the main
function.
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Nested Functions cont
 Like any .m-file function, a nested function
contains the usual components of an .m-file
function.
 However, a nested function must always
terminate with an end statement.
 In fact, if an .m-file contains at least one
nested function, then all functions, including
subfunctions, in the file must terminate with
an end statement
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Example  Nested Function
 This example assigns a function handle for a
nested function and then passes the handle to
the MATLAB function fminbnd to find the
minimum point on a parabola.
 The ConcaveUp fcn constructs and returns a
function handle f for the nested function p.
This handle gets passed to fminbnd.
function f = ConcaveUp(a, b, c)
f = @p;
function y = p(x)
y = a*x^2 + b*x + c;
end
end
Bruce Mayer, PE
Engineering/Math/Physics 25: Computational Methods
35
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Example  Nested Function cont
 Test the Nest in the Command Window
>> g = ConcaveUp(7, 41, -73);
>> fminbnd(g, -50, 50)
ans =
-2.9286
 Note than the function
p(x) can see the
variables a, b, and c
in the calling
function’s workspace.
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Nested vs Sub Functions

Nested functions might seem to be the same
as subfunctions, but they are not. Nested
functions have two unique properties:
1. A nested function can access the workspaces of
all functions inside of which it is nested. Thus,
– a variable that has a value assigned to it by the primary
function can be read or overwritten by a function nested
at any level within the main function
– A variable assigned in a nested function can be read or
overwritten by any of the functions containing that
function.
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt
Nested vs Sub Functions cont

The second unique property:
2. If you construct a function handle for a nested
function, the handle not only stores the
information needed to access the nested function;
it also stores the values of all variables shared
between the nested function and those functions
that contain it.
– This means that these variables persist in memory
between calls made by means of the function handle.
Engineering/Math/Physics 25: Computational Methods
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-25_Functions-4.ppt