Correlation analysis, correlation is a term that is a measure of the strength of a linear relationship between two quantitative variables.

Pearson’s Product-Moment Correlation

One of the most common measures of correlation is Pearson’s product-moment correlation, which is commonly referred to simply as the correlation, or just the letter r.

Correlation shows the strength of a relationship between two variables and is expressed numerically by the correlation coefficient.

Naïve Bayes Classification in R

Correlation Analysis

The correlation coefficient r measures the strength and direction of a linear relationship,

•   1 indicates a perfect positive correlation.
• -1 indicates a perfect negative correlation.
•    0 indicates that there is no relationship between the different variables.

Values between -1 and 1 denote the strength of the correlation, as shown in the example below.

In this tutorial, we will explain the different ways of executing correlation plots in R

Cormorant Package

# remotes::install_github(“r-link/corrmorant”)

library(corrmorant)
library(tidyverse)
library(dplyr)

We are selecting only quantitative variables for further analysis

mpg<-select(mpg,displ,cyl,cty, hwy)
corrmorant(mpg, style = "binned") +
  theme_dark() +
  labs(title = "Correlations")

Customized Plot from ggcorrm

ggcorrm(data = mpg) +
  lotri(geom_point(alpha = 0.5)) +
  lotri(geom_smooth()) +
  utri_heatmap() +
  utri_corrtext() +
  dia_names(y_pos = 0.15, size = 3) +
  dia_histogram(lower = 0.3, fill = "grey80", color = 1) +
  scale_fill_corr() +
  labs(title = "Correlation Plot")

Visualize correlation matrix using corrplot

Following plots, correlation coefficients are colored according to the value. The correlation matrix can be also reordered according to the degree of association between variables.

How to learn statistics?

library(corrplot)
library(RColorBrewer)
M <-cor(mpg)
corrplot(M, method="circle")

corrplot(M, method="pie") 

Difference between association and correlation

corrplot(M, method="color")

corrplot(M, method="number")

There are three types of layout :

• “full” (default) : display full correlation matrix
• “upper”: display upper triangular of the correlation matrix
• “lower”: display lower triangular of the correlation matrix

corrplot(M, type="upper")

corrplot(M, type="lower") 

Types of data visualization charts

corrplot(M, type="upper", order="hclust")

Using different color spectrum

Sample size calculation in R

col<- colorRampPalette(c("red", "white", "blue"))(20)
corrplot(M, type="upper", order="hclust", col=col)

Change background color to lightblue

corrplot(M, type="upper", order="hclust", col=c("black", "white"),
         bg="lightblue")

Changing the color of the plot

Random Forest Feature selection in R

corrplot(M, type="upper", order="hclust",
         col=brewer.pal(n=8, name="PuOr"))

Changing the color and the rotation of text labels

corrplot(M, type="upper", order="hclust", tl.col="black", tl.srt=45)

Customize the corrplot

Handling Imbalanced data in R

col <- colorRampPalette(c("#BB4444", "#EE9988", "#FFFFFF", "#77AADD", "#4477AA"))
Specialized the insignificant value according to the significant level
corrplot(M, type="upper", order="hclust",
         p.mat = p.mat, sig.level = 0.01)
corrplot(M, method="color", col=col(200), 
         type="upper", order="hclust",
         addCoef.col = "black", # Add coefficient of correlation
         tl.col="black", tl.srt=45, #Text label color and rotation

sjPlot Package

sjp.corr( data, title = NULL, axis.labels = NULL, sort.corr = TRUE, decimals = 3, na.deletion = c("listwise", "pairwise"), corr.method = c("pearson", "spearman", "kendall"), geom.colors = "RdBu", wrap.title = 50, wrap.labels = 20,sjp.corr 65 show.legend = FALSE, legend.title = NULL, show.values = TRUE, show.p = TRUE, p.numeric = FALSE )

sjplot is very useful for small number of variables.

ggside in R

library(sjPlot)
sjp.corr(mpg,title ="Spearman Correlation",decimals =2)

PerformanceAnalytics Package

library(PerformanceAnalytics)
chart.Correlation(mpg, histogram=TRUE, pch="+")

Correlation plots are the best way to show the pattern and relationship.

Decision Trees in R

If you have utilized some other correlation plot please mention in the comment box will include the same.

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