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Random numbers

Random numbers . Generating Random Numbers. Generating random numbers rand() is another one of those versatile functions x=rand; x=rand(); %some keep the () to remind themselves it is a function-call vs. a variable name. x=rand(1); %avoid, it’s overdoing it…

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Random numbers

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  1. Random numbers

  2. Generating Random Numbers • Generating random numbers • rand() is another one of those versatile functions x=rand; x=rand(); %some keep the () to remind themselves it is a function-call vs. a variable name. x=rand(1); %avoid, it’s overdoing it… x=rand(2); %a 2-rows by 2-columns matrix x=rand(2,5); %a 2-rows by 5-columns matrix 

  3. rand() and a little bit of algebra: +- • What happens to a number k between 0 and 1 if it is added to another number? For example: What can we say about: 2+k ? What can we say about: k-4 ? >> The interval shifts left/right. k 1 0 k 0 2 1 3

  4. rand() and a little bit of algebra: */ • What happens to a number k between 0 and 1 if it is multiplied by another number? For example: What can we say about: 5*k ? What can we say about: k/2 ? >> The interval grows/shrinks. k 0 1 k 0 5

  5. End of algebra • So.. Using a combination of arithmetic operators, how would you generate these values (both excluded): k1 = rand_______________________; k2 = rand_______________________; k1 k2 15 -5.5 20 5.5

  6. Conclusion • To generate 1 float in the interval : ]a,b[ k = rand*(b-a)+a; This is not a formula worth remembering.. Just remember algebra!

  7. Example1 Thermometer A new thermometer is being built. In addition to showing the temperature, the manufacturer also wants to indicate a warning if the temperature is above or equal to 104 degrees Fahrenheit. You are being paid ($$$) to develop the program that will eventually be within the thermometer. It’s been a year, and still no thermometer.. How long are you going to wait???

  8. Example2 Rockets 0/1’s? • How about rockets??? How does software get written? Do we waste a rocket each time? • During launch, so many sensors give back information!!! • A couple of them are…. • Doors locked? True/False • Oxygen flowing properly? True/False • Fuel being delivered to engine? True/False

  9. Wrapping up • Vocabulary • Function call • Arguments • Collecting • Return-values • Versatile • New notions • Generating random numbers • Generating 1 random float value • Manipulating it to desire random range wanted • Generating a zero/one to simulate false/true • Examples • Temperature: rand() • Rocket: rand() and ceil()!!

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