Hello,
Inline.
Em 02-10-2013 15:16, rolf.kem...@renesas.com escreveu:
Hello Rui,
thanks a lot for the quick and exhaustive reply !
It shows that my understanding of DF is totally wrong.
I'm familiar with relational DBs where the columns of table have specific data
types.
Hence , I thought a DF collum is always of one specific type and the rows are
just an index equal to all columns.
Right. In a df, each column is a vector, therefore all elements are of
the same type.
In particular , what you call FACTORS is something new to me. I have nod idea
of statistics , but looking into several examples it looks like very
useful to me.
A factor corresponds to the statistical concept of categorical variable.
They are internally coded as integers, with a levels attribute, giving
the several categories of the factor.
What is the best reference manual to get a better imagination of how a DF is
implemented and what can I do with c() function ?
The doc I found so-far is not very exhaustive.
Try the R project home page, http://www.r-project.org. There's a link to
several manuals, on the lower left.
Rui Barradas
Thanks a lot
R. Kemper
Rolf Kemper, Manager, Mixed Signal Design, Networking, Renesas Electronics
Europe GmbH, , Arcadiastr. 10, 40472, Duesseldorf, Germany, Phone:+49 211
6503-1475, Fax:+49 211 6503-1540, mailto:rolf.kem...@renesas.com,
http://www.renesas.eu
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From: Rui Barradas <ruipbarra...@sapo.pt>
To: rolf.kem...@renesas.com,
Cc: r-help@r-project.org
Date: 10/01/2013 08:38 PM
Subject: Re: [R] Basic help on DF creation row by row
Hello,
The main problem is in the way you form newRow. You can't mix data
classes in a vector created with c(), so all its elements become
characters, the least common denominator:
newRow <- c("primitiveSpace", 1.1 , "mm2")
newRow
[1] "primitiveSpace" "1.1" "mm2"
Then when you rbind it with the data frame, they are all converted to
factors. This is because the default behavior is to have the option
stringsAsFactors set to TRUE. Try to check it:
options()$stringsAsFactors # TRUE
Now, each of those factors was created with only one level, so when you
try to assign something different to them, with the second rbind, NAs
are generated.
The correct way would be something like the following.
newRow <- data.frame(item = "primitiveSpace", value = 1.1 , unit = "mm2")
deviceSummary <- rbind(deviceSummary , newRow )
print(deviceSummary)
str(deviceSummary) # to check what you have
newRow <- data.frame(item = "primitiveCellSpace", value = 2.2 , unit =
"mm2")
deviceSummary <-rbind(deviceSummary , newRow )
print(deviceSummary )
Hope this helps,
Rui Barradas
Em 01-10-2013 14:24, rolf.kem...@renesas.com escreveu:
Dear Experts
I'm very new to R and after some days or reading and testing I tried to make
my first small application (and failed ...)
In general I would like to work with sqldf , ggplot2 to create some graphical
output.
At present I got stuck with this:
PROG
#############################################################################
deviceSummary <- data.frame(item = character(0) , value = numeric(0) , unit =
character(0) )
print ( sapply(deviceSummary, class))
newRow <- c("primitiveSpace", 1.1 , "mm2")
deviceSummary <-rbind(deviceSummary , newRow )
print(deviceSummary)
newRow <- c("primitiveCellSpace", 2.2 , "mm2")
deviceSummary <-rbind(deviceSummary , newRow )
print(deviceSummary )
OUTPUT
############################################################################
item value unit
"factor" "numeric" "factor"
X.primitiveSpace. X.1.1. X.mm2.
1 primitiveSpace 1.1 mm2
X.primitiveSpace. X.1.1. X.mm2.
1 primitiveSpace 1.1 mm2
2 <NA> <NA> mm2
Warning messages:
1: In `[<-.factor`(`*tmp*`, ri, value = "primitiveCellSpace") :
invalid factor level, NA generated
2: In `[<-.factor`(`*tmp*`, ri, value = "2.2") :
invalid factor level, NA generated
Inserting the first record went fine , but the next one will fail as you can
see.
Repeating only the first one (value1.1) went fine.
May be my imagination of DF is totally wrong. Hope someone can guide me.
Thanks a lot
Rolf
Rolf Kemper, Manager, Mixed Signal Design, Networking, Renesas Electronics
Europe GmbH, , Arcadiastr. 10, 40472, Duesseldorf, Germany, Phone:+49
211
6503-1475, Fax:+49 211 6503-1540, mailto:rolf.kem...@renesas.com,
http://www.renesas.eu
This message is intended only for the use of the address...{{dropped:24}}
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