## Wednesday, 2 October 2013

### Using Matlab Functions

• See list in book, or below, or follow the link to the full online list of Matlab functions
• Check help ( or helpwin ) on elmat, elfun, specfun, randfun
• Use "lookfor" to search for functions
• Click on the "Fx" function icon on the left edge of the Matlab command window, if available.
• Matlab trig functions sin, cos, tan assume angles in radians, just like C++
• sind, cosd, tand assume angles in degrees
• Some functions return multiple results
• A = [ 1, 2, 3; 4, 5, 6 ]
• size( A ) % returns [ 2, 3 ]
• [ nrows, ncols ] = size( A ); % stores results in nrows and ncols
• Some functions' results vary with dimension of input:
• max( 1-D vector ) returns a single maximum value.
• [ value, position ] = max( 1-D vector ) returns the maximum and its position
• max( 2-D matrix ) returns a row vector containing the max of each column
• max( max( 2-D matrix ) ) returns the maximum value in the matrix.
• ( As does max( 2-D_matrix( : ) ) )
• Common Matlab Functions. Note that many of the aggregating functions ( e.g. max, min, mean ) return a row vector of the operation applied on each column separately when applied to a matrix. A few functions worth noting:
• ( See the Function Browser in Matlab help for a more complete list, or read the help documentation on a particular subject such as linear algebra. )
• abs
• acos
• acosh
• asin
• asinh
• atan
• atan2( y, x ) - Arctangent of y / x, between -pi and pi.
• atanh
• ceil - smallest integer that exceeds its argument. ceil( 3.1 ) is 4, ceil( -3.9 ) is -3.
• clock - time and date in a six-element vector.
• cos
• cosh
• cot
• csc
• cumsum - cumulative sum, i.e. cumsum( [ 1 2 3 4 ] ) yields [ 1 3 6 10 ].
• date
• exp - exponential, base e.
• fix - nearest integer towards zero. fix( 3.9 ) is 3, fix( -3.9 ) is -3.
• fix - nearest integer towards zero. fix( 3.9 ) is 3, fix( -3.9 ) is -3.
• floor - largest integer not exceeding its argument - floor( 3.9 ) is 3, floor( -3.1 ) is -4.
• length - number of elements in a vector, or number of columns in a matrix.
• log - natural logarithm
• log10 - base 10 logarithm.
• max - Maximum. When applied to a matrix, yields a vector with the maximums of each column.
• mean - Average. See max.
• min - Minimum. See max.
• mod( X, Y ) - returns X - n.*Y where n = floor(X./Y). Like mod in C, but works with all types of numbers.
• pow2 - Two raised to the power of the argument.
• prod - product of the elements of its argument. prod( [ 2 3 5 ] ) is 30.
• rand - generates pseudo-random numbers in the range of [ 0, 1 ).
• Initialize the random number generator ONCE with rand( 'state', sum( 100*clock))
• realmax - largest positive floating point number ( for this installation on this computer. )
• realmin - smallest positive floating point number ( same ).
• rem( x, y ) - remainder when x is divided by y.
• Strictly speaking, returns x - ( y * fix( x / y ) ), which defines actions for negative and non-integer operands.
• round - rounds off to nearest integer. round( 3.5 ) = 4, round( -3.5 ) = -4.
• size - Returns all dimensions of its argument, e.g. number of rows and number of columns for a 2-D matrix.