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Diffstat (limited to 'matrices/script.rst')
| -rw-r--r-- | matrices/script.rst | 40 |
1 files changed, 22 insertions, 18 deletions
diff --git a/matrices/script.rst b/matrices/script.rst index 646da8f..4e57f99 100644 --- a/matrices/script.rst +++ b/matrices/script.rst @@ -51,7 +51,7 @@ All matrix operations are done using arrays. Thus all the operations on arrays are valid on matrices also. A matrix may be created as, :: - m1 = matrix([1,2,3,4]) + m1 = array([1,2,3,4]) .. #[Puneeth: don't use ``matrix``. Use ``array``. The whole script will @@ -70,10 +70,16 @@ A list can be converted to a matrix as follows, :: l1 = [[1,2,3,4],[5,6,7,8]] - m2 = matrix(l1) + m2 = array(l1) -Note that all matrix operations are done using arrays, so a matrix may -also be created as +{{{ switch to next slide, exercise 1}}} + +Pause here and create a two dimensional matrix m3 of order 2 by 4 with +elements 5, 6, 7, 8, 9, 10, 11, 12. + +{{{ switch to next slide, solution }}} + +m3 can be created as, :: m3 = array([[5,6,7,8],[9,10,11,12]]) @@ -100,17 +106,16 @@ subtraction. Now let us try, m3 * m2 -Note that in arrays ``array(A) star array(B)`` does element wise -multiplication and not matrix multiplication, but unlike arrays, the -operation ``matrix(A) star matrix(B)`` does matrix multiplication and -not element wise multiplication. And in this case since the sizes are -not compatible for multiplication it returned an error. +Note that in arrays ``m3 * m2`` does element wise multiplication and not +matrix multiplication, -And element wise multiplication in matrices are done using the -function ``multiply()`` +And matrix multiplication in matrices are done using the function ``dot()`` :: - multiply(m3,m2) + dot(m3, m2) + +but due to size mismatch the multiplication could not be done and it +returned an error, {{{ switch to next slide, Matrix multiplication (cont'd) }}} @@ -126,11 +131,10 @@ matrix m1 is of the shape one by four, let us create another one of the order four by two, :: - m4 = matrix([[1,2],[3,4],[5,6],[7,8]]) - m1 * m4 + m4 = array([[1,2],[3,4],[5,6],[7,8]]) + dot(m1, m4) -thus unlike in array object ``star`` can be used for matrix multiplication -in matrix object. +thus the function ``dot()`` can be used for matrix multiplication. {{{ switch to next slide, recall from arrays }}} @@ -158,7 +162,7 @@ Now let us try to find out the Frobenius norm of inverse of a 4 by 4 matrix, the matrix being, :: - m5 = matrix(arange(1,17).reshape(4,4)) + m5 = arange(1,17).reshape(4,4) print m5 The inverse of a matrix A, A raise to minus one is also called the @@ -177,7 +181,7 @@ And the Frobenius norm of the matrix ``im5`` can be found out as, :: sum = 0 - for each in array(im5.flatten())[0]: + for each in im5.flatten(): sum += each * each print sqrt(sum) |