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Plot Group Means and Confidence Intervals - R Base Graphs


Previously, we described the essentials of R programming and provided quick start guides for importing data into R.


Here, we’ll describe how to create mean plots with confidence intervals in R.


Pleleminary tasks

  1. Launch RStudio as described here: Running RStudio and setting up your working directory

  2. Prepare your data as described here: Best practices for preparing your data and save it in an external .txt tab or .csv files

  3. Import your data into R as described here: Fast reading of data from txt|csv files into R: readr package.

Here, we’ll use the R built-in ToothGrowth data set.

Data

head(ToothGrowth)
##    len supp dose
## 1  4.2   VC  0.5
## 2 11.5   VC  0.5
## 3  7.3   VC  0.5
## 4  5.8   VC  0.5
## 5  6.4   VC  0.5
## 6 10.0   VC  0.5

Plot group means

The function plotmeans() [in gplots package] can be used.

library(gplots)
# Plot the mean of teeth length by dose groups
plotmeans(len ~ dose, data = ToothGrowth, frame = FALSE)

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# Add mean labels (mean.labels = TRUE)
# Remove line connection (connect = FALSE)
plotmeans(len ~ dose, data = ToothGrowth, frame = FALSE,
          mean.labels = TRUE, connect = FALSE)

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Infos

This analysis has been performed using R statistical software (ver. 3.2.4).


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