- Programming club interest meeting
- Thursday (Feb. 25), 5:00 PM
- Bailey 101
- Exam 1
- Next Wednesday (Mar. 2)
- Material since beginning of semester (e.g., expressions, variables, vectors, plotting, matrices, functions, scripts, etc.)
- 3 - 5 short-answer questions, may include writing short pieces of Matlab
- Sample exam now available
- Whole class period (50 minutes)
- Open references (book, notes, computer); closed person
- Sections 9.1 - 9.3
- 2d array
- To create:
arrayname = [ [row1]; [row2]; … ] - Linear vs row-column indexing
arrayname ( position )arrayname ( row, column )
- Operators similar to those for vectors - lists in book
- Examples
>> % Matrix of how many miles 3 people walked on 3 days >> miles = [ [ 1.0, 1.0, 1.0 ]; [ 2.0, 2.0, 2.0]; [ 3.0, 3.0, 3.0 ] ] miles = 1 1 1 2 2 2 3 3 3 >> % Fix the 1st person’s 2nd day distance >> miles(1,2) = 10 miles = 1 10 1 2 2 2 3 3 3 >> % Linear indexing >> miles( 5 ) ans = 2 >> % Convert to kilometers and (for no plausible reason) take the square roots >> kms = miles .* 1.6 kms = 1.6000 16.0000 1.6000 3.2000 3.2000 3.2000 4.8000 4.8000 4.8000 >> sqrt( kms ) ans = 1.2649 4.0000 1.2649 1.7889 1.7889 1.7889 2.1909 2.1909 2.1909
- Handout
- Matrix multiplication and geometric transformations
- Draw a simple triangle
>> vertices = [ [0, 0, 4]; [0, 3, 0] ] vertices = 0 0 4 0 3 0 >> plot( vertices(1,:), vertices(2,:) ) >> % Oops, this didn’t close the triangle. Add a 4th vertex to do that >> vertices(1,4) = 0 vertices = 0 0 4 0 0 3 0 0 >> plot( vertices(1,:), vertices(2,:) ) >> % Make axes extend far enough to make triangle visible >> axis( [-1, 5, -1, 4 ] ) - Now make the triangle bigger
>> scale = [ [2, 0]; [0, 3] ] scale = 2 0 0 3 >> vertices2 = scale * vertices vertices2 = 0 0 8 0 0 9 0 0 >> hold on >> plot( vertices2(1,:), vertices2(2,:), 'r' ) >> axis( [ -1, 9, -1, 10 ] )
- Draw a simple triangle
- Building big matrices from small
- Read sections 9.4 and 11.8