{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

14-440-127+Lecture+03

# 14-440-127+Lecture+03 - 14:440:127 Introduction to...

This preview shows pages 1–3. Sign up to view the full content.

14:440:127– Introduction to Computers for Engineers Notes for Lecture 03 Rutgers University, Spring 2010 Instructor- Blase E. Ur 1 Strings Character strings do something interesting when you try to put them into a vector. The following example motivates our exploration of the subject: a = ’hello’; b = ’goodbye’; c = [a b] c = ’hellogoodbye’ c(2) = ’e’ As you see, placing two strings in a vector effectively combines them into one long string. This is because strings themselves are actually vectors of single characters, and thus we are combining two shorter vectors into one long vector. Since character strings in Matlab are simply vectors of single characters, any operation we perform on vectors can also be used on a string: a = ’I love Matlab’; a(3:6) = ’hate’ ans = ’I hate Matlab’ a((end-2):end) = [] % deletes those values % by setting them to the ‘empty vector’ ans = ’I hate Mat’ fliplr(a) ans = ’taM etah I’ Also note that to include an apostrophe in a string, use two single quotes next to each other i.e. ’matlab’’s stupid’ Now what if we wanted to create a data type analogous to a vector, but for strings? 1.1 Cell Arrays A cell array is a type of array (matrix) in which each element can be a vector or matrix itself. Since character strings are vectors, a cell array essentially allows us to make a ‘pseudo-vector’ of strings. However, the syntax for a cell array differs slightly from a vector. Rather than using square brackets to define a cell array, we instead use squigly braces– { and } . To access individual elements, we again use squigly braces rather than parentheses. However, to copy/change/move parts of the cell array, we use parentheses as normal. Here’s an example: a = { ’one’ ’two’ ’three’ }; % squigly braces b = a(2:3); % note that parentheses are used % this is because we are copying parts of the array fprintf(’The number is %s \n’, b{2} ) % note squigly braces The number is three 1.2 String Comparison- strcmp Because strings are actually vectors of characters, funny things happen when you try to compare two strings using the == double equals signs. If the strings are the same length, this works (giving you a vector of 1’s and 0’s as the 1

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
result). However, if the strings aren’t the same length, you get an error. To compare strings more easily, there’s a function called strcmp – string comparison. If returns either 1 or 0 (true or false) whether the strings are the same, case sensitive. thislecture = ’blah blah blah’; if(strcmp(thislecture,’brilliant insights’)) disp(’job well done’) else disp(’waste of tuition money’) end 2 Element by Element Math Operations on Matrices Mathematical operations on Matrices can be a bit tricky since there are multiple ways in which operations such as multiplication can be defined mathematically on matrices. However, other operations such as addition and subtraction are much simpler since they operate ‘element by element.’ 2.1 Add, Subtract
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 12

14-440-127+Lecture+03 - 14:440:127 Introduction to...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online