Previously, we described the essentials of R programming and provided quick start guides for importing data into **R**. We also showed how to **visualize** data using R base graphs.

Here, we’ll present the basics **lattice** package, which is a powerful and elegant data visualization system that aims to improve on base R graphs.

# Installing and loading the lattice package

```
# Install
install.packages("lattice")
# Load
library("lattice")
```

# Main functions in the lattice package

xyplot() |
Scatter plot |

splom() |
Scatter plot matrix |

cloud() |
3D scatter plot |

stripplot() |
strip plots (1-D scatter plots) |

bwplot() |
Box plot |

dotplot() |
Dot plot |

barchart() |
bar chart |

histogram() |
Histogram |

densityplot |
Kernel density plot |

qqmath() |
Theoretical quantile plot |

qq() |
Two-sample quantile plot |

contourplot() |
3D contour plot of surfaces |

levelplot() |
False color level plot of surfaces |

parallel() |
Parallel coordinates plot |

wireframe() |
3D wireframe graph |

Note that, other functions (**ecdfplot**() and **mapplot**()) are available in the **latticeExtra** package.

# xyplot(): Scatter plot

**R function**: The R function **xyplot**() is used to produce bivariate scatter plots or time-series plots. The simplified format is as follow:

`xyplot(y ~ x, data)`

```
my_data <- iris
head(my_data)
```

```
## Sepal.Length Sepal.Width Petal.Length Petal.Width Species
## 1 5.1 3.5 1.4 0.2 setosa
## 2 4.9 3.0 1.4 0.2 setosa
## 3 4.7 3.2 1.3 0.2 setosa
## 4 4.6 3.1 1.5 0.2 setosa
## 5 5.0 3.6 1.4 0.2 setosa
## 6 5.4 3.9 1.7 0.4 setosa
```

**Basic scatter plot**: y ~ x

```
# Default plot
xyplot(Sepal.Length ~ Petal.Length, data = my_data)
```

```
# Color by groups
xyplot(Sepal.Length ~ Petal.Length, group = Species,
data = my_data, auto.key = TRUE)
```

```
# Show points ("p"), grids ("g") and smoothing line
# Change xlab and ylab
xyplot(Sepal.Length ~ Petal.Length, data = my_data,
type = c("p", "g", "smooth"),
xlab = "Miles/(US) gallon", ylab = "Weight (1000 lbs)")
```

**Multiple panels by groups**: y ~ x | group

```
xyplot(Sepal.Length ~ Petal.Length | Species,
group = Species, data = my_data,
type = c("p", "smooth"),
scales = "free")
```

# cloud(): 3D scatter plot

```
my_data <- iris
head(my_data)
```

```
## Sepal.Length Sepal.Width Petal.Length Petal.Width Species
## 1 5.1 3.5 1.4 0.2 setosa
## 2 4.9 3.0 1.4 0.2 setosa
## 3 4.7 3.2 1.3 0.2 setosa
## 4 4.6 3.1 1.5 0.2 setosa
## 5 5.0 3.6 1.4 0.2 setosa
## 6 5.4 3.9 1.7 0.4 setosa
```

**Scatter 3D plot**: z ~ x * y

```
# Basic 3D scatter plot
cloud(Sepal.Length ~ Sepal.Length * Petal.Width,
data = iris)
```

```
# Color by groups; auto.key = TRUE to show legend
cloud(Sepal.Length ~ Sepal.Length * Petal.Width,
group = Species, data = iris,
auto.key = TRUE)
```

# Box plot, Dot plot, Strip plot

```
ToothGrowth$dose <- as.factor(ToothGrowth$dose)
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
```

**Basic plot**: Plot len by dose

```
# Basic box plot
bwplot(len ~ dose, data = ToothGrowth,
xlab = "Dose", ylab = "Length")
# Violin plot using panel = panel.violin
bwplot(len ~ dose, data = ToothGrowth,
panel = panel.violin,
xlab = "Dose", ylab = "Length")
# Basic dot plot
dotplot(len ~ dose, data = ToothGrowth,
xlab = "Dose", ylab = "Length")
# Basic stip plot
stripplot(len ~ dose, data = ToothGrowth,
jitter.data = TRUE, pch = 19,
xlab = "Dose", ylab = "Length")
```

**Plot with multiple groups**: Additional argument **layout** is used: c(3, 1) specifying the number of column and row, respectively

```
# Box plot
bwplot(len ~ supp | dose, data = ToothGrowth,
layout = c(3, 1),
xlab = "Dose", ylab = "Length")
# Violin plot
bwplot(len ~ supp | dose, data = ToothGrowth,
layout = c(3, 1), panel = panel.violin,
xlab = "Dose", ylab = "Length")
# Dot plot
dotplot(len ~ supp | dose, data = ToothGrowth,
layout = c(3, 1),
xlab = "Dose", ylab = "Length")
# Strip plot
stripplot(len ~ supp | dose, data = ToothGrowth,
layout = c(3, 1), jitter.data = TRUE,
xlab = "Dose", ylab = "Length")
```

# Density plot and Histogram

```
densityplot(~ len, data = ToothGrowth,
plot.points = FALSE)
histogram(~ len, data = ToothGrowth,
breaks = 20)
```

- Plot with multiple groups

```
densityplot(~ len, groups = dose, data = ToothGrowth,
plot.points = FALSE, auto.key = TRUE)
```

# Infos

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

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