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HW1

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									     Weizmann 2011-2012          Introduction to Matlab & Data Analysis


Exercise #1
E-mail for submission and questions: ariel.gispan@weizmann.ac.il
Please read the submission guidelines (in the course website)
carefully, before doing the task.


Question 1: simple display
   1. Write your name into the variable myName.
   2. Display myName to the screen.
   3. Pause for 0.3 seconds
   4. Display your favorite movie quote.
   5. Pause for 0.3 seconds.


Question 2: matlab questions
Note: some of matlabs functions display text on the screen (regardless of semi-colon).
In these cases don‟t try to use the disp command.
   1. Write your age into a variable called „myAge‟.
   2. Display the following „my age is <myAge>‟. You must use matlab sprintf
        command in order to display complex input (contains both numeric and text).
   3.   What is the difference between the who,whos commands ? What is the
        output of both of them in your pc?
   4.    List MATLAB files in folder using matlab specific function(find out which
        one).
   5.   This ex is annoying. Ask matlab why (repeat it 5 times)…
   6. Repeat section 5 two more times.


Question 3: matrix manipulations
Please read matlab‟s introduction to matrices
   1. Create the variable „n‟ with a value of 5.
   2. Create a matrix with n rows and n columns that is a magic square ( = equal
        row, column, and diagonal sums).
   3. Let‟s check that this is a magic square . Display the column-wise and row-
        wise sum of M.
   4. Flip the matrix left to right (first column become last etc…).
 Weizmann 2011-2012             Introduction to Matlab & Data Analysis


5. M is a 2-D matrix with a size of 5X5. Each entry has two coordinates, row and
   column. Display the content of M in the 3rd column, 4th row, using double
   index (two coordinates).
6. In matlab you can refer M as a 1-D matrix in length of 25. Just access it with a
   single index ( one coordinate). What single index is equivalent to the double
   index in the previous question? What is the general formula for this
   conversion? (in terms of i,j,m,n : (i,j) – the double index in a mXn matrix ).
7. The indices (1,1),(2,2),(3,3)… are the indices that are on the diagonal. Create a
   vector d that is the single index representation of those diagonal indices (with
   the command: d=a:b:c, figure out which a,b,c will fit here).
8. Compute the sum of elements that are on the diagonal, using d, and display it.
9. Assign the value 3 to the first row, only columns 3,4,5 (use the colon
   operator).
10. Assign the value 2 to all the second column (use the colon operator) .
11. Remove the 5th row from M.
12. Assign the variables m = #matrix rows ,n=#matrix columns. Don‟t type it
   explicitly but use matlab function that returns the matrix size. Display the new
   matrix size: “The new size of M is mXn” using sprint. Of course you must
   replace the characters m,n with their value.
13. Display the size of M using sprintf:. Don‟t just write 4X5, but enter the
   variable
14. Compute the mean of the columns of M and display it. The answer is a matrix
   with size of 1X5
15. Matrix multiplication:

                         - it is possible only if the number of columns in B is
   equal to the number of rows in C. A has the same rows number as in B and the
   same columns number as in C. The formula is



                                   . Repeat the same as in 14, but this time do it
   through matrix multiplication – find the other matrix that is required that will
   yield the same result as in 14 (hint: the result A is a matrix with the same
   columns number as M, so M is the matrix from the right – so you must find
   the matrix from the left).

								
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