[R] convert microns to nm in a messy dataset

[Ivan Calandra]

Dear John,

Thank you for your answer.
However, it does not make sense to me, as it works only line by line of the
data.frame, and I need something for "last observation carried forward" as Peter
mentioned. The script does not work as is either, probably due to typos with
semi-colons and "if... else" statements, so I cannot really test it.

Best,
Ivan

--
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

On May 10, 2019 at 3:47 PM John McKown <john.archie.mckown using gmail.com> wrote:

>  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 <http://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
> <mailto: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
> > <https://www.researchgate.net/profile/Ivan_Calandra>
> >
> >    ______________________________________________
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> > http://www.R-project.org/posting-guide.html
> > <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
>