[R] convert microns to nm in a messy dataset

[John McKown]

This is my approach. It is based entirely on what you said (multiply by
1000 to convert from nm to µm, but I think it is divide by). It assumes
that the starting value is in µm. If the starting value is in nm, change
the "factor=1" to "factor=1000". That µm is micro-meters (10^-6) and nm is
nano-meters (10^-9), so divide by would be correct.

 factor=1;
 for (i in 1:length(my.data$V19)) {
 print("Start");print(factor);print(my.data[i,]);
 if (my.data$V19[i] == "nm") { factor=1000;
my.data$V19[i]="µm";print("nm");} else if (my.data$V19[i] == "µm")
{factor=1;};
 if (suppressWarnings(!is.na(as.numeric(my.data$V19[i])))) { my.data$V19[i]
= as.character(as.numeric(my.data$V19[i]) * factor); print("changed"); }
 print(factor);print(my.data[i,]);print("End");



On Fri, May 10, 2019 at 6:54 AM Ivan Calandra <calandra using rgzm.de> wrote:

> Dear useRs,
>
> Below is a sample of my dataset (I have more rows and columns).
>
> As you can see in the 2nd column, there are values, the name of the
> parameter
> ('Sq' in that case), some integer ('45' in that case) and the unit ('µm' or
> 'nm').
> I know how to extract the rows of interest (those with values), but they
> are
> expressed in different units. All values following a line with the unit are
> expressed in that unit, but the number of lines is not constant (sometimes
> each
> value is expressed in a different unit so there will be a new unit line,
> but
> there are sometimes several values in a row expressed in the same unit so
> without unit lines in between). I hope this is clear (it should be with the
> example provided).
> This messy dataset comes from an external software so I don't have any
> means to
> format the ways the data are collated. I have to find a way to deal with
> it in
> R.
>
> What I would like to do is convert the values in nm to µm; I just need to
> multiply by 1000.
>
> What I don't know is how to identify the values that are expressed in nm
> (all
> values that follow a line with 'nm' until there is a line with 'µm').
>
> I don't even know how I should search online because I don't know how this
> kind
> of operation is called.
> Any help is appreciated.
>
> Thank you in advance.
> Ivan
>
>
> my.data <- structure(list(V1 = c("2019/05/10", "#", "#", "#", "2019/05/10",
> "2019/05/10", "2019/05/10", "#", "#", "#", "2019/05/10", "#", "#", "#",
> "2019/05/10", "#", "#", "#", "2019/05/10", "2019/05/10"), V19 =
> c("0.2012800083", "45", "Sq", "µm", "0.3634383236", "0.4360454777",
> "0.3767733568", "45", "Sq", "nm", "102.013048", "45", "Sq", "µm",
> "0.1413840498", "45", "Sq", "nm", "65.4459715", "46.45802917")), row.names
> =
> c(NA, 20L), class = "data.frame")
>
> --
> Dr. Ivan Calandra
> TraCEr, laboratory for Traceology and Controlled Experiments
> MONREPOS Archaeological Research Centre and
> Museum for Human Behavioural Evolution
> Schloss Monrepos
> 56567 Neuwied, Germany
> +49 (0) 2631 9772-243
> https://www.researchgate.net/profile/Ivan_Calandra
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
This is clearly another case of too many mad scientists, and not enough
hunchbacks.


Maranatha! <><
John McKown

	[[alternative HTML version deleted]]