CMPS 1371 Introduction to Computing for Engineers

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CMPS 1371Introduction to Computing for Engineers

• VECTORS

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ARRAYS

• The real strength of Matlab is in matrix
  manipulations
• Arrays are homogeneous collection of things.
• All are the same
• Are indexable

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VECTORS

• Our simplest array type is called a vector.
• Simple example
• ODDS 1 3 5 7 9 11 13 15
• To index a vector, need to know the position
  within the vector
• First element has position 1 (NOT ZERO!)
• ODDS(1) 1
• Last element either the length of the array or
  the special label end
• ODDS(8) 15
• ODDS(end) 15

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Create a Vector
To create a row vector, enclose a list of values
in brackets
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Create a Vector
You may use either a space or a comma as a
delimiter in a row vector
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Create a Vector
Use a semicolon as a delimiter to create a new row
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Shortcuts

• While a complicated matrix might have to be
  entered by hand, evenly spaced matrices can be
  entered much more readily. The command 
• b 15
• or the command
• b 15
• both return a row matrix 

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Increments
The default increment is 1, but if you want to
use a different increment put it between the
first and final values
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To calculate spacing

• Use linspace

number of elements in the array
Final value in the array
Initial value in the array
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Basic Functions

• Some basic functions
• Consider temp 1 2 3 4 5
• length(temp) 5
• sum(temp) 15
• mean(temp) 3
• median(temp) 3

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Calculations

• Matrices can be used in many calculations with
  scalars
• There is no confusion when we perform addition
  and subtraction
• Multiplication and division are a little
  different 
• In matrix mathematics the multiplication operator
  () has a very specific meaning regarding Matrix
  multiplication
• We will use (.) for matrix multiplication
• We can use () for scalar multiplication

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Adding Vectors
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Adding Vectors
Addition between arrays is performed on
corresponding elements
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Multiplying Vectors
Multiplication between arrays is performed on
corresponding elements if the . operator is used
MATLAB interprets to mean matrix
multiplication. The arrays a and b are not the
correct size for matrix multiplication in this
example
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Array Operations

• Array multiplication .
• Array division ./
• Array exponentiation .

In each case the size of the arrays must match
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Changing the Vector

• Easy to add elements to the array
• Temp 1 2 3 4
• Temp(5) 8 ? Temp now has 5 elements 1, 2, 3,
  4, 8
• Can also concatenate
• fred 1,2,3,4 3,4,5,
• fred fred 4 5 6 7
• Can also remove elements by using the "Null"
  vector
• A 1 2 3 4 5 6 7
• A(2) now what is A