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General Computer Science for Engineers CISC 106 Lecture 04 James Atlas Computer and Information Sciences 6/17/2009 Lecture Overview If statements Logical Operators Matlab Output Data Structures Arrays IF Statements Review IF Statements Nested if statements can be used when two things have to be true for a command to execute IF Statements Using nested if statements if (x < 5) if ( x > 2) y = 500 else y = 300 else y= 200 end IF Statements Using nested if statements if (x < 5) if ( x > 2) y = 500 else y = 300 else y= 200 end Using multiple conditions in one if statement if ( x < 5 & x > 2) y = 500 else y = 200 end Logical Operators - AND & && Logical Operators - OR | || Logical Operators - NOT ~ Matlab Output ◦ How do we see information about what is going on in our program? Matlab Output ◦ How do we see information about what is going on in our program? ◦ disp() Matlab Output Formatted Output Example: ◦ “There are 5 widgets in inventory” ◦ fprintf(‘There are %d widgets in inventory’, widgets); Matlab Output Formatted Output Example: ◦ “There are 5 widgets in inventory” ◦ fprintf(‘There are %d widgets in inventory’, widgets); %d acts as a place holder for widget variable at end of command and is known as a conversion character. Conversion characters specify the notation of the output. Note the variable widgets as the second argument. Matlab Output Lets look at the syntax ◦ count = fprintf(fid, format, A, ...) ◦ count – the number of bytes written ◦ fid – refers to opened file ◦ format – is a format string in between single quotes If fid is set to one or omitted the output goes to the screen. What if my program is too complex? Matlab Debugging Break Data Structures So far we have only talked about single points of data Data Structures Structured data ◦ Defines how multiple pieces of data relate to each other Data Structures Structured data ◦ Defines how multiple pieces of data relate to each other We actually have covered one data structure already Arrays Arrays Arrays Fundamental unit of data in MATLAB Collection of data into rows and columns (MATrix LABoratory) 1 dimensional, vector 2 dimensional, matrix 0 dimensional, scalar (a 1x1 array) Row vector, column vector , transpose Arrays Array commands a = [1 2 3 4] b = [1; 2; 3; 4] c = [1 2; 3] (error) d = [1 2; 3 4] f = d(1,2) g(4,5) = 7 Arrays continued zeros(), ones(), eye() scalar vs. array arithmetic +, - , * (.*) , / (./) ^ etc.