- Sections 5.1 - 5.6
- Matrices, arrays
- Matlab treats single numbers as 1×1 arrays
- Vector = 1D array
- Write with brackets and commas
- Double colon to create vector
linspaceandlogspacealso create vectors- Indexing with parentheses to access elements
- Dot operators to operate on arrays
- Examples / practice
- Create an array containing the number of characters in each person’s name
in your row, and manipulate some elements
>> letters = [ 7, 5, 6 ] letters = 7 5 6 >> letters(1) ans = 7 >> letters(3) = letters(3) - 2 letters = 7 5 4 - Vectors vs scalar variables as abstractions of memory
- Both abstract the idea of storage locations, vectors are just many contiguous
locations rather than a single isolated one
- Both abstract the idea of storage locations, vectors are just many contiguous
locations rather than a single isolated one
- How does indexing work if you have more than 1 dimension?
- You can do both multi-dimensional indexing as in matrices in math, or
“linear indexing” along concatenated columns (more on this when we
talk about matrices)
>> table = [1 2 3; 10 20 30] table = 1 2 3 10 20 30 >> table(1,2) ans = 2 >> table(4) ans = 20
- You can do both multi-dimensional indexing as in matrices in math, or
“linear indexing” along concatenated columns (more on this when we
talk about matrices)
- More examples
>> % Leap years from 2000 to 2099 >> [2000 : 4 : 2099] ans = Columns 1 through 5 2000 2004 2008 2012 2016 Columns 6 through 10 2020 2024 2028 2032 2036 Columns 11 through 15 2040 2044 2048 2052 2056 Columns 16 through 20 2060 2064 2068 2072 2076 Columns 21 through 25 2080 2084 2088 2092 2096 >> [2099 : -4 : 2000] ans = Columns 1 through 5 2099 2095 2091 2087 2083 Columns 6 through 10 2079 2075 2071 2067 2063 Columns 11 through 15 2059 2055 2051 2047 2043 Columns 16 through 20 2039 2035 2031 2027 2023 Columns 21 through 25 2019 2015 2011 2007 2003 >> [2096 : -4 : 2000] ans = Columns 1 through 5 2096 2092 2088 2084 2080 Columns 6 through 10 2076 2072 2068 2064 2060 Columns 11 through 15 2056 2052 2048 2044 2040 Columns 16 through 20 2036 2032 2028 2024 2020 Columns 21 through 25 2016 2012 2008 2004 2000 >> % Table of squares of numbers from 1 to 10 >> % ...with exponentiation >> [1:10] .^ 2 ans = 1 4 9 16 25 36 49 64 81 100 >> linspace(1,10,10) .^ 2 ans = 1 4 9 16 25 36 49 64 81 100 >> [1:10] ^ 2 {Error using ^ Inputs must be a scalar and a square matrix. To compute elementwise POWER, use POWER (.^) instead.} >> %... with multiplication >> [1:10] .* [1:10] ans = 1 4 9 16 25 36 49 64 81 100 >> [1:10] * [1:10] {Error using * Inner matrix dimensions must agree.} >> % Calculate hypotenuses of many triangles at once (after single-triangle example) >> a = 3; b = 4; >> sqrt( a^2 + b^2 ) ans = 5 >> as = [ 3, 5, 73.6 ]; >> bs = [ 4, 12, 9]; >> sqrt( as .^ 2 + bs .^ 2 ) ans = 5.0000 13.0000 74.1482
- Create an array containing the number of characters in each person’s name
in your row, and manipulate some elements
- Vector lab
- Advanced ways of indexing arrays and manipulating elements
- Read sections 5.7 - 5.9