2.12: Summary of important R code
- Page ID
- 33225
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The main components of R code used in this chapter follow with components to modify in lighter and/or ALL CAPS text, remembering that any R packages mentioned need to be installed and loaded for this code to have a chance of working:
- summary(DATASETNAME)
- Provides numerical summaries of all variables in the data set.
- summary(lm(Y ~ X, data = DATASETNAME))
- Provides estimate, SE, test statistic, and p-value for difference in second row of coefficient table.
- confint(lm(Y ~ X, data = DATASETNAME), level = 0.95)
- Provides 95% confidence interval for difference in second row of output.
- 2
*
pt(abs(Tobs), df = DF, lower.tail = F)- Finds the two-sided test p-value for an observed 2-sample t-test statistic of
Tobs
.
- Finds the two-sided test p-value for an observed 2-sample t-test statistic of
- hist(DATASETNAME$Y)
- Makes a histogram of a variable named
Y
from the data set of interest.
- Makes a histogram of a variable named
- boxplot(Y ~ X, data = DATASETNAME)
- Makes a boxplot of a variable named Y for groups in X from the data set.
- pirateplot(Y ~ X, data = DATASETNAME, inf.method = “ci”, inf.disp = “line”)
- Requires the
yarrr
package is loaded. - Makes a pirate-plot of a variable named Y for groups in X from the data set with estimated means and 95% confidence intervals for each group.
- Add
theme = 2
if the confidence intervals extend outside the density curves and you can’t see how far they extend.
- Requires the
- mean(Y ~ X, data = DATASETNAME); sd(Y ~ X, data = DATASETNAME)
- This usage of
mean
andsd
requires themosaic
package. - Provides the mean and sd of responses of Y for each group described in X.
- This usage of
- favstats(Y ~ X, data = DATASETNAME)
- Provides numerical summaries of Y by groups described in X.
-
Tobs
<-
coef(lm(Y ~ X, data = DATASETNAME))[2]; Tobs
B<-
1000
Tstar<-
matrix(NA, nrow = B)
for (b in (1:B)){
lmP<-
lm(Y ~ shuffle(X), data = DATASETNAME)
Tstar[b]<-
coef(lmP)[2]
}- Code to run a
for
loop to generate 1000 permuted versions of the test statistic using theshuffle
function and keep track of the results inTstar
- Code to run a
- pdata(Tstar, abs(Tobs), lower.tail = F)
- Finds the proportion of the permuted test statistics in Tstar that are less than -|Tobs| or greater than |Tobs|, useful for finding the two-sided test p-value.
-
Tobs
<-
coef(lm(Y ~ X, data = DATASETNAME))[2]; Tobs
B<-
1000
Tstar<-
matrix(NA, nrow = B)
for (b in (1:B)){
lmP<-
lm(Y ~ X, data = resample(DATASETNAME))
Tstar[b]<-
coef(lmP)[2]
}- Code to run a
for
loop to generate 1000 bootstrapped versions of the data set using theresample
function and keep track of the results of the statistic inTstar
.
- Code to run a
- qdata(Tstar, c(0.025, 0.975))
- Provides the values that delineate the middle 95% of the results in the bootstrap distribution (
Tstar
).
- Provides the values that delineate the middle 95% of the results in the bootstrap distribution (