### -----------------------------------------------------------------------
### Autor: Paul Fink, et. al. (Stand: SoSe 2017)
### -----------------------------------------------------------------------


## ----setup-folien-7------------------------------------------------------
daten <- chickwts
ges <- factor(sample(c("m", "f"), size = 71, replace = TRUE))

## ----varnames------------------------------------------------------------
names(daten)

## ----df-var-zugriff-list-------------------------------------------------
daten$weight

## ----df-var-zugriff-matrixname-------------------------------------------
daten[, "weight"]

## ----df-var-zugriff-matrixidnex------------------------------------------
daten[, 1]

## ----df-beob-zugriff-matrixindex-----------------------------------------
daten[c(1, 4, 20), ]

## ----df-beob-zugriff-matrix----------------------------------------------
daten[daten$feed == "casein", ]

## ----df-beob-zugriff-subset----------------------------------------------
subset(daten, feed == "casein")

## ----df-subset-----------------------------------------------------------
subset(daten, feed == "casein")
subset(daten, feed %in% c("casein", "linseed"))
subset(daten, (feed == "casein") & (weight > 240))

## ----df-var-zufuegen-list------------------------------------------------
daten$gender <- ges

## ----df-var-zufuegen-dataframe-------------------------------------------
daten <- data.frame(daten,ges)

## ----df-var-zufuegen-cbind-----------------------------------------------
daten <- cbind(daten,ges)

## ----df-var-zufuegen-matrix----------------------------------------------
daten[, 3] <- ges

## ----df-var-loeschen-list------------------------------------------------
daten$gender <- NULL

## ----df-var-loeschen-matrix----------------------------------------------
daten <- daten[, -3]

## ----df-var-aendern------------------------------------------------------
# 1. Variable aus data.frame in Hilfsobjekt speichern
h <- daten[,"weight"]
# 2. Aenderungen am Hilfsobjekt durchfuehren
h <- h / 1000
# 3. Hilfsobjekt als Variable in data.frame aufnehmen
daten[,"weight"] <- h 

## ----df-var-aendern-transform--------------------------------------------
# Alle Schritte laufen intern ab
daten <- within(daten, {weight <- weight / 1000})