Offlist comments No reply needed .. This is just for emphasis and
clarification.
On Dec 9, 2010, at 11:19 AM, Jon Erik Ween wrote:
David
I see how findInterval is a more elegant way of doing 1). I'd need
to change the indices in the lookup table, as
findInterval(36, c(0, 17, 19, 24, 29, 34, 44, 54, 64, 69, 74, 79,
84, 89) )
[1] 6
should be 7, not 6. The age range for the 7th column 35-44. But
that's easy.
As you say, changing the output to agree with your expectations is
"easy" but to be clear, R _is_ delivering the correct response to the
question "which interval is 36 located in ... the 6th. Any ambiguity
is due to your not formulating a good question (and my errors).
I can't see how findInterval will help me for 2), though.
"2)" was never very clear. I do think findInterval must be what is
needed, but I am repeating my call for you to post a full example and
more complete explanation to the list.
The standard score is integer and not a range.
Which is _not_ how statisticians usually think of a "z score". So it
may need some further background or use of less misleading
terminology. You are probably tasked with using a table handed to you
that at one time was a "z-score" for <something> but has been recast
in tabular form.
--
David.
So it maps 1 to 1. The real problem, though, is setting the value in
the main dataframe (df) with the value from the lookup table based
on the identified age and score indices.
My initial guess was:
df$DSTz <-DSTzlook[which(DSTzlook[,1]==df
$Agetmp),which(DSTzlook[1,]==df$DSF+df$DSB)]
which could be rewritten:
df$DSTz <-DSTzlook[which(DSTzlook[,1]== findInterval(df$Age, c(0,
17, 19, 24, 29, 34, 44, 54, 64, 69, 74, 79, 84,
89))),which(DSTzlook[1,]==df$DSF+df$DSB)]
But it is the indirect referencing of the lookup in the main table
that causes me trouble.
Jon
Soli Deo Gloria
Jon Erik Ween, MD, MS
Scientist, Kunin-Lunenfeld Applied Research Unit
Director, Stroke Clinic, Brain Health Clinic, Baycrest Centre
Assistant Professor, Dept. of Medicine, Div. of Neurology
University of Toronto Faculty of Medicine
Kimel Family Building, 6th Floor, Room 644
Baycrest Centre
3560 Bathurst Street
Toronto, Ontario M6A 2E1
Canada
Phone: 416-785-2500 x3648
Fax: 416-785-2484
Email: jw...@klaru-baycrest.on.ca
Confidential: This communication and any attachment(s) may contain
confidential or privileged information and is intended solely for
the address(es) or the entity representing the recipient(s). If you
have received this information in error, you are hereby advised to
destroy the document and any attachment(s), make no copies of same
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On 2010-12-09, at 11:06 AM, David Winsemius wrote:
On Dec 9, 2010, at 10:51 AM, Jon Erik Ween wrote:
Thanks David
What I am trying to do is set up a script that assigns z-scores to
a large dataframe (2500x300, but has Age in years and test scores
as columns.) from a published table of age-corrected standard
scores on this cognitive test.
1) The age intervals in the lookup table are given and not my
choice.
You may want to skip the intermediate translation to the row and
column labels and just use the results of findInterval:
findInterval( 16, c(0, 17, 19, 24, 29, 34, 44, 54, 64, 69, 74, 79,
84, 89) )
[1] 1
findInterval( 90, c(0, 17, 19, 24, 29, 34, 44, 54, 64, 69, 74, 79,
84, 89) )
[1] 14
Those look like appropriate indices for the column argument
2) Sorry I didn't post an example table, it looks something like
this ("Age" is in the first row, standard scores in the first
column):
17 19 24 29 34 44 ....
30 2.6 2.6 2.6 2.6 2.6 2.6
29 1.8 1.8 1.8 2.0 2.6 2.6
28 1.0 1.0 1.8 1.8 2.6 2.6
27 0.0 0.5 1.0 1.8 2.6 2.6
26 -.5 0.0 0.0 1.0 1.8 2.6
.
.
.
.
So, if a subject (row) has age==29 and a standard score of 28, the
value should be 1.8, etc.
Looks like a job for two findInterval indices to be used used with
"[ r , c ] ".
--
David.
Thanks
Jon
Soli Deo Gloria
Jon Erik Ween, MD, MS
Scientist, Kunin-Lunenfeld Applied Research Unit
Director, Stroke Clinic, Brain Health Clinic, Baycrest Centre
Assistant Professor, Dept. of Medicine, Div. of Neurology
University of Toronto Faculty of Medicine
Kimel Family Building, 6th Floor, Room 644
Baycrest Centre
3560 Bathurst Street
Toronto, Ontario M6A 2E1
Canada
Phone: 416-785-2500 x3648
Fax: 416-785-2484
Email: jw...@klaru-baycrest.on.ca
Confidential: This communication and any attachment(s) may contain
confidential or privileged information and is intended solely for
the address(es) or the entity representing the recipient(s). If
you have received this information in error, you are hereby
advised to destroy the document and any attachment(s), make no
copies of same and inform the sender immediately of the error. Any
unauthorized use or disclosure of this information is strictly
prohibited.
On 2010-12-09, at 10:33 AM, David Winsemius wrote:
On Dec 9, 2010, at 9:34 AM, Jon Erik Ween wrote:
Hi
This is (hopefully) a bit more cogent phrasing of a previous
post. I'm
trying to compute a z-score to rows in a large dataframe based
on values in
another dataframe. Here's the script (that does not work). 2
questons,
1) Anyone know of a more elegant way to calculate the "rounded"
age value
than the nested ifelse's I've used?
2) how to reference the lookup table based on computed indices?
Thanks
Jon
# Define tables
DSTzlook <-
read.table("/Users/jween/Documents/ResearchProjects/ABC/data/
DSTz.txt",
header=TRUE, sep="\t", na.strings="NA", dec=".", strip.white=TRUE)
df<-stroke
# Compute rounded age.
df$Agetmp
<-ifelse(df$Age>=89,89,ifelse(df$Age>=84,84,ifelse(df
$Age>=79,79,ifelse(df$Age>=74,74,ifelse(df$Age>=69,69,ifelse(df
$Age>=64,64,ifelse(df$Age>=54,54,ifelse(df$Age>=44,44,ifelse(df
$Age>=34,34,ifelse(df$Age>=29,29,ifelse(df$Age>=24,24,ifelse(df
$Age>=19,19,17))))))))))))
Ew, painful. If you want categorized ages (since what the above
coding is producing is not "rounded" in any sense of that word as
I understand it, then why not findInterval() as an index into the
ages you wnat to label these case with?
df$Agetmp <- c(17,19,24,29,34,44,54,64,69,74,79,84)[ # note
Extract operation
findInterval(runif(100,0,100),
c(17,19,24,29,34,44,54,64,69,74,79,84,110) )
] # close extraction
The other option, of course, and a more "honest" one in this
instance would be
cut(vec, breaks=c(...), labels=c(...) )
(It's not clear why you are not picking midpoint ages within
those brackets to me.)
# Reference the lookup table based on computed indices
df$DSTz
<-DSTzlook[which(DSTzlook[,1]==df$Agetmp),which(DSTzlook[1,]==df
$DSF+df$DSB)]
I have not been able to figure out what you are trying to do
here. Trying to use a 2d lookup looks promising a a way to
emulate what an Excel user might attempt, but an example (as
requested in the message at the bottom of every posting) would
really be of great help in making this more concrete for those of
us with insufficient abstractive abilities.
--
David.
# Cleanup
#rm(df)
#df$Agetmp<-NULL
--
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Sent from the R help mailing list archive at Nabble.com.
David Winsemius, MD
West Hartford, CT
David Winsemius, MD
West Hartford, CT
David Winsemius, MD
West Hartford, CT
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