EENG 2101 Matlab for Engineers

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EENG 2101Matlab for Engineers

• Introduction to programming in Matlab
• Matlab input and output
• input statement
• variableinput(Enter a value )
• The prompt string between single quotes will be
  printed and Matlab will wait for the user to
  enter a value.
• variableinput(Enter a value )
• Suppresses echoing variable to screen

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EENG 2101Matlab for Engineers

• Introduction to programming in Matlab
• Matlab program output
• Most simple form of output is to type the
  variable name.
• x25 x will cause the value of x to be
  printed
• x5 10 15 20 25
• x
• x
• 5 10 15 20 25
• disp statement disp(x)
• 5 10 15 20 25

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EENG 2101Matlab for Engineers

• Introduction to programming in Matlab
• Formatted output fprintf statement
• fprintf(format_string, variable(s))
• fprintf(Gain f dB,gain)
• Prints the string Gain followed by the value
  of gain in fixed-point notation.
• fprintf(Gain f dB\n,gain)
• Prints the string Gain followed by the value
  of gain in fixed-point notation and a line feed.

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EENG 2101Matlab for Engineers

• Introduction to programming in Matlab
• Other formats that may be specified by the
  placeholder
• e prints in scientific notation
• g uses the shorter of fixed-point or
  scientific notation
• Width and precision fields may be included to
  specify the number of characters to be printed in
  a numerical result and the location of the
  decimal point in either fixed-point or scientific
  notation.
• 7.2f 7 total characters (width), 2 after
  decimal point

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EENG 2101Matlab for Engineers

• Introduction to programming in Matlab
• Matlab programs are of two typesscripts and
  functions
• Scripts
• sequences of Matlab executable statements
• stored as files with the extension .m
• invoked by typing the name of the file without
  extension
• require no arguments
• return no results

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EENG 2101Matlab for Engineers

• Introduction to programming in Matlab
• Functions
• sequences of Matlab executable statements
• stored as files with the extension .m
• require arguments
• return results to the calling environment
• require standard syntax
• function outvar fname(invar)
• where invar is the input variable, outvar is
  the output variable, fname is the function name
  (which must be the same as the file name)

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EENG 2101Matlab for Engineers

• Example cosine function that accepts arguments
  in degrees
• function ydcos(phi)
• ycos(phipi/180)
• Using this function
• dcos(30) returns the cosine of 30
• zdcos(-120) assigns cos(-120) to z
• Adcos(010360) vector input and output
• Local variables variables used within functions
  are local to those functions and are not
  accessible from outside the function.

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EENG 2101Matlab for Engineers

• Functions with multiple inputs and/or outputs
• function outvar1, outvar2, fname (invar1,
  invar2)
• Matlab treats lines beginning with as
  comments. Comment lines immediately following
  the function declaration and prior to the first
  Matlab command are printed when help fname is
  typed.
• function ydcos(phi)
• ydcos(phi) computes the cosine of angle phi
  whose
• value is given in degrees
• ycos(phi180/pi)

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EENG 2101Matlab for Engineers

• Rules for writing functions
• The first line must be the function declaration
  listing the keyword function, the output
  variable(s), the function name (which must match
  the file name), and the input variable(s)
• Use comments!
• Be careful in writing functions with more than
  one input argument that the proper matrix
  operators are used.
• function retvalexpcos(a,w,t)
• will work if a, w, and t are all scalars
• but will produce an error message if t is a
  matrix
• retvalexp(-at)cos(wt)

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EENG 2101Matlab for Engineers

• Matlab relational operators
• lt Less than lt Less than or equal to
• gt Greater than gt Greater than or equal to
• Equal to Not equal to
• x3 y4 x lt y
• Returns a value of 1, indicating TRUE.
• x3 5 7 y9 -1 7 x y
• Returns 0 0 1 indicating that the last elements
  in x and y are the same, but the other elements
  in x differ from y.

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EENG 2101Matlab for Engineers

• Matlab logical operators
• AND OR NOT
• Example
• x y z gt4
• x3, y5, z2
• x2 1 2 y1 1 1 z6 3 1
• x9 0 7 y 8 0 7 z3 4 5

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EENG 2101Matlab for Engineers

• Matlab find command returns the indices of
  nonzero elements in a vector x.
• voltage12.4 12.4 12.5 11.9 10.8 12.1
  12.4
• low_voltagesfind(voltagelt12.0)
• fault_voltagesvoltage(low_voltages)
• The find function will return either an element
  number or, if called with two returned values,
  will supply the indices in row and column form.

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EENG 2101Matlab for Engineers

• Matlab if, and else commands
• if ltlogical statementgt
• Matlab executable statements
• end
• if ltlogical statementgt
• Matlab executable statements
• else
• Matlab executable statements
• end

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EENG 2101Matlab for Engineers

• Matlab elseif command
• if ltlogical statementgt
• Matlab executable statements
• elseif ltlogical statementgt
• Matlab executable statements
• elseif ltlogical statementgt
• Matlab executable statements
• else
• Matlab executable statements
• end

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EENG 2101Matlab for Engineers

• Matlab for loops
• for indexexpression
• Matlab executable statements
• end
• for k110
• Matlab statements (executed 10 times)
• end

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EENG 2101Matlab for Engineers

• Matlab while loops
• while logical_expression
• Matlab executable statements
• end
• The loop repeats until the logical expression
  becomes false (i.e., becomes zero) program flow
  then passes to the statement following the end.