Normalize a column

[#1]

TLDR: How do I normalize a column to itself?

See attached. I have:

• Column A = 0,1,2,3. Maybe think of this as like an ID number
• Column B. Think of this as a timestamp
• Column C. This is the data

Now I want column D to have the data in Column C, ONLY when B=1.

As you can see in the attached file, I have manually copy-pasted the yellow cells from C into D. Pasted over and over.

Therefore when I do D/C, I'm basically normalizing the whole of column C, to these special yellow values. This is the reason I'm doing all this, is to find D/C. So a value of 0.9 in this column means C is lower than the yellow C's, and 1.1 means it's higher than the yellow C's. 

So, long story short, what is the formula that goes in D, to be able to get the yellow values?

[#2]

edit

Sorry, I need to pay more attention.  You weren't asking how to get D/C.

Select C and D, then right click.  New Formula Column > Combine > Ratio (reverse order)

[#3]

Sorry if I'm still misunderstanding, but if you want D to be missing when B is not 1 and D to have the values of C when B is one, try this formula.

Choose( :B, :C, . )

[#4]

Thanks for your answer. Not exactly. I simply want a formula in column D, that will reproduce those numbers.

That formula will take the yellow cells in C, and apply it to the entire column D. So that now the entire column D is the repeated yellow cells as shown. (Presumably in the formula somewhere, we would hardcode B=1.)

Probably I confused things by manually typing in D in the example. I manually typed in those numbers, but I want a formula that will populate D for me.

[#5]

Thanks for your answer, but here is a comparison of your answer, and what I want which is just a formula for D. So compare the final column and D and you'll see they are not the same.

[#6]

Isn'1 the formula just

If( :B == 1, 1, :D / :C )