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Using Matlab as a Research Tool

2. Matrix operations, save/load, script files, user functions

Hanselman & Littlefield: Chapters 4 (Script M-files), 12 (Functions), 14 (File and directory
management), 18 (Data analysis)

Matrix functions that operate by column
– sum, mean, prod
– cumsum, cumprod
– operations on vectors
– grand sums, means, etc.
– operating by row via double transposition

M-files (script files)
– global variables
– comments
– Ex: write MatrixTotals as a script file

M-files (functions)
– sample functions: LogSpiral, AnovaIsotonic
– global vs. local variables
– function, return
– input arguments
– output arguments
– comments
– help documentation

Ex: MatrixTotals, CricketChirpsToTemp, TimeConvert, GetLineParams, RandomIntegers

Elements of a well-written function
– help documentation
 – name and purpose of function
 – usage
 – descriptions of input and output variables
– meaningful function and variable names in standardized format
– indentation and comments (becomes more important later)
– blank lines separating groups of related statements
– error-checking up front, with meaningful error messages

Saving and loading
– diary
 – diary fname
 – diary on, off
– save [matfile]
 – save [fname.mat]
 – save fname
 – save fname [vars]
– save [ascii]
 – save fname [vars] -a
– load [matfile]
 – load [fname.mat]
 – load fname
– load [ascii]
 – load xxx.yyy, produces a matrix xxx
– xlsread(‘filename’)
– “copy and paste” instead of load