# [R] Multiplying two vectors of the same size to give a third vector of the same size

@vi@e@gross m@iii@g oii gm@ii@com @vi@e@gross m@iii@g oii gm@ii@com
Tue Jun 20 17:55:08 CEST 2023

```Phil,

What have you tried. This seems straightforward enough.

Could you clarify what you mean by NULL?

In R, it is common to use NA or a more specific version of it.

So assuming you have two vectors containing floats with some NA, then:

C <- A*B

Will give you the products one at a time if the lengths are the same. NA
times anything is NA.

Your second condition is also simple as you want anything below a threshold
to be set to a fixes value.

threshold <- 0.1
C < threshold

The last line returns a Boolean vector you can use to index C to get just
the ones you select as TRUE and thus can change:

Result <- C[C < threshold]

And you can of course do all the above as a one-liner.

Is that what you wanted?

-----Original Message-----
From: R-help <r-help-bounces using r-project.org> On Behalf Of Philip Rhoades via
R-help
Sent: Tuesday, June 20, 2023 11:38 AM
To: r-help using r-project.org
Subject: [R] Multiplying two vectors of the same size to give a third vector
of the same size

People,

I am assuming that what I want to do is easier in R than say Ruby.

I want to do what the Subject says ie multiply the cells in the same
position of two vectors (A and B) to give a result in the same position
in a third vector (C) BUT:

- The values in the cells of A and B are floats between 0.0 and 1.0 or
NULL

- If there is a NULL in the multiplication, then the result in the cell
for C is also a NULL

- If there is a value less than (say) 0.01 in the multiplication, then
the result in the cell for C is 0.0

Any suggestions appreciated!

Phil.

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E-mail:  phil using pricom.com.au

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