SUNY Geneseo Department of Mathematics

Vector Operations

Friday, February 6

Math 230 02
Spring 2015
Prof. Doug Baldwin

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Previous Lecture

Misc
- Math colloquium
  - Dickerson, “Mathematics Majors’ Understandings of the Concept of Mathematical Definition”
  - Monday, Feb. 9 4:00 - 5:00, Newton 201
  - Extra credit for going and writing summary/reaction
Questions?
Operations on Vectors
- Sections 2.2 and 2.3
  - Things you can get from vectors
  - e.g., sign, minimum, max, sum of vectors, product, cumulative sums and products
    - Apply down columns of matrices
  - Multiplying vectors by scalars
  - Array operations, e.g, adding elements of vectors
    - Raising to power via “.^”
- “Map” and “reduce”
  - Map = apply some operation element-by-element to all elements of one or more arrays, producing array of results
    - For example array operations, e.g., +, .*, .^, etc.
  - Reduce = apply some operation to all elements of a single array in order to reduce that array to a single value
    - For example min, max
  - Given 2 vectors containing children’s heights last year and this year, compute the pairwise differences (i.e., how much each child grew)
    - Map or reduce? Map
    - Matlab expression?
```
>> h2014 = [ 46 51 45 ];
>> h2015 = [51 53 50];
>> h2015 - h2014
ans =
    5     2     5
```
  - Given a vector containing the monthly profits of some company, compute the total profit
    - Map or reduce? Reduce
    - Matlab expression?
```
>> profits = [ 1200 1600 1350 1400 ];
>> sum( profits )
ans =
    5550
```
  - Given the vectors of children’s heights, compute the average amount of growth
    - Map or reduce?
      - Both—map to compute growth followed by reduce to calculate average
    - Matlab expression?
```
>> mean( h2015-h2014 )
ans =
    4
```
Vectors Lab
- Handout
Next
- Scripts
- Read section 3.2
- Optional video “Writing a Simple Script” at http://www.see.ed.ac.uk/teaching/courses/matlab/unit03/simple-script.shtml

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