Useful operators, commands, and concepts for this unit…
rand(), round(), floor() (round down), ceil() (round up), repmat(), random numbers, random ordering of numbers
clear all before starting on these exercises. Keep some notes on what’s going on and try to understand each step and then move on to the next section
x = 1:10
e = rand(1,10)
s = x+e
% single numbers
round(0.5)
round(0.49)
round(0.51)
% ... and vectors
round(e)
round(s)
% and a slightly different ways
floor(s) % to the nearest integer down
ceil(s) % to the nearest integer up
Create a column vector r of size 100 that contains randomly chosen 0 or 1, each with equal probability.
Create another column vector s of size 100 that contains randomly chosen 0 (with p=0.3) and 1 with p=0.7).
Look at the help for the function randperm. Create a randomly permuted vector idx of size 10, and a vector q that contains 5 zeros followed by 5 ones. Can you think of a simple way to permute the entries q using idx.
Now repeat the previous exercise but re-write the code such that the size of idx can be controlled by a variable n. Are there any things to watch out for here?
X that has 50 rows and 3 columns. Column 1 should contain 1..50. Column 2 should contain 1^2..50^2 and Column 3, √1..√50.To motivate some of these exercises with something that’s a bit closer to a real-life situation:
Open the following text file that contains
a column of data. You can make an empty variable, say z by assigning an empty list to it: z = []. Then open it in the variable viewer and paste the contents of the text file into it.
Can you figure out how to (interactively) make a plot of those numbers?
Scripts and functions - why they are useful, how they work.