Predefined MATLAB Functions ELEC 206 Computer Applications for Electrical Engineers Dr. Ron Hayne

206_M32 Elementary Math Functions abs(x) sqrt(x) sign(x) round(x), fix(x) ceil(x), floor(x) rem(x,y) exp(x) log(x), log2(x), log10(x)

206_M33 Trigonometric Functions  Angle in radians(180 degrees = pi radians) sin(x), cos(x), tan(x) asin(x), acos(x), atan(x)  Angle in degrees sind(x), cosd(x), tand(x) asind(x), acosd(x), atand(x) angle_deg = angle_rad*(180/pi); angle_rad = angle_deg*(pi/180);

206_M34 Data Analysis Functions  Minimum and Maximum max(x), [a,b]=max(x), max(x,y) min(x), [a,b]=min(x), min(x,y)  Averages median(x), mean(x), std(x)  Sums and Products sum(x), prod(x) cumsum(x), cumprod(x)

206_M35 Data Analysis Functions  Sorting sort(x)  Size size(x), [a,b]=size(x) length(x)

206_M36 Random Numbers  Uniform Random Numbers rand('seed',n), rand(n), rand(m,n) Interval 0 to 1 Interval a to b x = (b - a)*r + a;  Gaussian Random numbers randn('seed',n), randn(n), randn(m,n) Normal Distribution Mean = 0, Standard Deviation = 1.0 Modified Distribution Mean = b, Standard Deviation = a x = a*r + b;

206_M37 Problem Solving Applied  Weather Data Problem Statement Using the data in the file Weather_Data.xls, find the total monthly precipitation, the total precipitation for the year, and the day on which it rained the most. Input/Output Description Total Monthly Precipitation Total Precipitation Weather_Data.xls Day of Most Rain

206_M38 Problem Solving Applied Hand Example 12x31 Matrix  Rows = Months  Columns = Days  Hundreths of inches  Invalid = tot_jan = 2.72 in tot_feb = 1.66 in tot_jan+feb = 4.38 in max = Jan

206_M39 Problem Solving Applied Algorithm Development Import spreadsheet into matrix Change values to 0 Interchange rows and columns Monthly Totals (inches) = sum columns/100 Yearly Total = sum Monthly Totals Find max and location

206_M310 MATLAB Solution

206_M311 MATLAB Solution clc % Example Weather Data % Find the total precipitation for each month, and % for the entire year, using a data file % wd=Weather_Data; wd(2,29)=0; % Change values to 0 wd(2,30)=0; wd(2,31)=0; wd(4,31)=0; wd(6,31)=0; wd(9,31)=0; wd(11,31)=0;

206_M312 MATLAB Solution % Use transpose operator to change rows to columns wd = wd'; % Sum of each column is sum for each month monthly_total = sum(wd)/100 % Find the annual total yearly_total = sum(monthly_total) % Find the annual maximum, and month [maximum_precip,month] = max(max(wd)); % Find the annual maximum, and day [maximum_precip,day] = max(max(wd')); % Print max data maximum_precip = maximim_precip/100 month day

206_M314 Manipulating Matrices  Defining Matrices A = [1 2 3; 4 5 6]; (2x3) A = [1 2 3; 4 5 6]; B = [1 2 3] (1x3) B = [ ]; C = [A; B] = [1 2 3; 4 5 6; 1 2 3]; (3x3)

206_M315 Manipulating Matrices  Changing Matrices D = [3 4 5]; D(2) = 8; D = D(5) = 7; D =

206_M316 Manipulating Matrices  Defining Matrices with the Colon Operator E = 1:4 E = F = 0.0:0.5:2.0 F =

206_M317 Manipulating Matrices  Extracting Data with the Colon Operator G = [1 2 3; 2 3 4; 3 4 5; 4 5 6]; x = G(3, :) x = y = G(:, 2:3) y =

206_M318 Manipulating Matrices  Extracting Data with the Colon Operator G = [1 2 3; 2 3 4; 3 4 5; 4 5 6]; G(3,2) ans = 4 G(7) ans = 4 G(:) ans =

206_M319 Computational Limitations  Double Range to  Exponent Overflow y = 2e200; y^2 ans = Inf  Exponent Underflow x = 2e-200 x/y ans = 0  Double Precision eps ans = e-016  Divide by Zero y/0 ans = Inf 0/0 ans = NaN

206_M320 Special Values and Functions  Special Values pi i j Inf NaN  Special Functions clock Year Month Day Hour Minute Seconds date dd-Mth-yyyy

206_M321 Summary  MATLAB Functions Math, Trig, Data Analysis, Random Numbers  Problem Solving Applied  Manipulating Matrices  Special Values and Functions  End of Chapter Summary MATLAB Summary Characters, Commands and Functions Key Terms