If you ever had to simulate random outcomes in excel sheet, you might have already heard of about the spreadsheet function rand(), this little function generates a random fraction between 0 and 1 whenever you use it. So I usually write = if I need a random number between 0 to 12. Of course, if you have analysis tool pack installed like I do, then we can use round(rand()*12,0)int(rand()*12)+1randbetween(0,12) to do the same.
In order to simulate a dice throw, thus you can use round(rand()*5,0)int(rand()*6)+1
So, what would you do if you need to simulate the face total when you throw 2 dice?
round(rand()*10,0)int(rand()*11)+2
Wrong
Why? Apparently a random number between 2 and 12 (1 is not possible as the minimum you can get when you throw two dice is 2) doesn’t simulate 2 dice throws properly.
The CORRECT way to do this is instead generate 2 individual random numbers and add them up, like:
round(rand()*5,0)int(rand()*6) + 1 + round(rand()*5,0)int(rand()*6) + 1
Here is why this is correct way to simulate dice throws using random number generator functions:
I have ran these 2 random functions each for 2500 times and plotted the distribution:
As you can see, the left plot of int(rand()*11)+2 tells that each of the 11 possibilities (2,3,4,5,6,7,8,9,10,11) are equally likely. But that is not what happens when you throw a dice, you see an awful lot more 5,6,7,8 than you see a perfect 12 or 2. And there is a reason for that, the distribution of 2 dice throws is actually a bell curve, and when you use int(rand()*6) + int(rand()*6) + 2 the distribution is bell curvish.
Update: Thanks to Jon for pointing out that round() is not the choice if you want random integers, you should use int instead. See his explanation in the comments and the illustration here.
I have used this logic to simulate monopoly board game and prove that it is not really that random.
More on games: Bingo / Housie ticket generator excel sheet
9 Responses to “Show forecast values in a different color with this simple trick [charting]”
While this works in a pinch, it clearly "lightens" the colors of the entire chart. Depending on where you use this, it will be blatantly obvious that you don't know what you are doing and present a poor looking graph.
Why not separate the data into different segments when charting and have as many colors as you have data points? You might have to create a new legend and/or repeat the chart in "invisible ink", but it would be cleaner and more consistent when new or updated data becomes available.
While I think I agree that doing it "properly" via a second series is preferable, I don't necessarily agree that making the entirety of the "future" (data, gridlines, and even the axis) semi-transparent is "poor looking". I think it could be seen as adding more emphasis to the "future-ness" of the forecast data.
In short, it's another tool for the toolbox, even if it's never needed.
Simply and clever 🙂
Quick & effective, cool. thanks.
I always use the dummy series.
Nice little trick, thanks very much!
Two sets of data better. Control is much better.
You can use the same chart next month to see what is actual and what is forecast.
To use this trick, I think grid lines has to be removed, that will make the graphic much more sharp.
to be honest, i dont understand why there is needed to do this way... in this case horizontal lines will be pale as well. then why a just can't change the color of the line partly???
Great tutorial. Thanks for the tutorial!