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

Philip Rhoades ph|| @end|ng |rom pr|com@com@@u
Tue Jun 20 19:04:24 CEST 2023

```avi,

On 2023-06-21 01:55, avi.e.gross using gmail.com wrote:
> Phil,
>
> What have you tried. This seems straightforward enough.
>
> Could you clarify what you mean by NULL?

I guess in R in would just be an empty cell? - ie NOT a zero.

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

Ah yes, that would be it I think.

> 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.

Right - yes that works! - thanks!

> 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]

Ah, I see . .

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

Yes.

> Is that what you wanted?

Exactly except I meant:

Result <- C[C > threshold]

Thanks!

Phil.

> -----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.
>
> --
>
> PO Box 896
> Cowra  NSW  2794
> Australia
> E-mail:  phil using pricom.com.au
>
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> ______________________________________________
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