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who
Shows variables that have been defined in this Command Window (just shows the names of the variables).
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whos
Shows variables that have been defined in this Command Window (this shows more information on the variables, similar to what is in the Workspace Window).
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clear
Clears out all variables so they no longer exist.
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clear variablenames
Clears out a particular variable.
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abs(variable)
Absolute value of that number or variable.
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fix(variable)
Round towards zero.
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floor(variable)
Round towards minus infinity.
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ceil(variable)
Round towards positive infinity.
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round(variable)
Round to nearest integer.
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sign(variable)
Returns 1 if number greater than zero; returns 0 if it is zero; returns -1 if less than zero.
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rem(num,div)
Returns the remainder from division (first number divided by the second number).
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char, logical, int32, double
char = used to store single characters or strings; logical = used to store true/false values; int32 = integer with max 32 bits; double = real number, can use floating point.
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rand
Generates a random real number from 0-1.
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How to generate a random integer in the range of x-y.
round(rand*(y-x))-x
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How to create a row vector or column vector
- Row vec: v = [1 2 3 4] or [1:4]; for steps, use colon operator.
- Column vec: v = [1;2;3;4]
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How to refer to an element in (a) a vector (b) a matrix?
- a) myvec(element#)
- b) mymat(row#,column#) - can refer to subsets of matrices (ex: mymat(1:2,2:3)). If a single index is used (ex: mymat(1)), it unwinds the matrix columnwise (goes down row by row until the next column).
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How to create a matrix.
mat = [4 3 1; 2 5 6; 3:5]
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zeros(rows, columns) ; zeros(#)
ones(rows, columns); ones(#)
Creates a matrix of zeroes (or ones) of the given dimensions; if only one number is given, that will be the number of rows and columns.
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length(variable)
Gives the number of elements in a vector and the length of the largest dimension (either rows or columns) in a matrix.
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size(variable)
Returns the numbers of rows and columns in a matrix (rows first, then columns).
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numel(variable)
Returns the total number of elements in an array (vector or matrix).
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variable(end,#)
end refers to the last element in a vector. vec(end) = vec(length(vec)). In a matrix, it can refer to the last element in a row or column. Ex: mymat(end,1) returns the last element of the first row and first column.
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reshape(variable,rows,columns)
Iterates through the matrix columnwise and returns a new matrix with the new dimensions.
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fliplr(variable)
Flips the matrix from left to right; the left-most column becomes the last column and so forth.
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flipud(variable)
Flips up to down. Works from outsides in. (1st becomes last, 2nd becomes 2nd to last, etc.)
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rot90(variable)
Rotates the matrix counterclockwise 90 degrees. The top-right value becomes the top-left value; last column becomes the first row.
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repmat(variable,m,n)
Creates a larger matrix, which consists of an m x n matrix of copies of the matrix named in the function call. Ex: a 2 x 2 matrix when called in repmat(mat,2,3) becomes a 6 x 4 matrix with repetitions of the original 2 x 2.
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Empty vector
[ ]; a vector that stores no values, created using empty brackets.
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