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How to convert multiple columns in an R data frame into a single numerical column along with a column having column names as factor?
When we receive data from any source, it is highly likely that it would not be a perfect data set for the intended analysis, therefore, we need to perform some cleaning or mining based on the characteristics of the data. For example, if we have a column name of a data frame as factor levels of a numerical variable then we might want to convert that data frame in such a way that numerical values are stored in a single column and the column names are stored in another column that will represent a factor so that we can apply the analysis of variance techniques on this type of data. For this purpose, we can use the stack function as shown in the below examples.
Example
Consider the below data frame −
x1<-rnorm(5) x2<-rnorm(5) x3<-rnorm(5) x4<-rnorm(5) df1<-data.frame(x1,x2,x3,x4) df1
Output
x1 x2 x3 x4 1 0.4231515 -0.02059351 -0.7323391 0.19199970 2 0.4816832 0.88382316 -0.5297544 0.17681651 3 -1.1703627 0.16328116 -0.7856500 0.03778934 4 -1.6009281 -0.93433554 1.5626258 -1.51384088 5 2.5075787 -0.94192579 -1.2340071 0.07821619
Stacking data frame df1 −
Example
df1<-stack(df1) df1
Output
values ind 1 0.42315154 x1 2 0.48168320 x1 3 -1.17036266 x1 4 -1.60092810 x1 5 2.50757869 x1 6 -0.02059351 x2 7 0.88382316 x2 8 0.16328116 x2 9 -0.93433554 x2 10 -0.94192579 x2 11 -0.73233913 x3 12 -0.52975443 x3 13 -0.78564997 x3 14 1.56262579 x3 15 -1.23400706 x3 16 0.19199970 x4 17 0.17681651 x4 18 0.03778934 x4 19 -1.51384088 x4 20 0.07821619 x4
Example
y1<-rpois(5,2) y2<-rpois(5,2) y3<-rpois(5,2) y4<-rpois(5,2) df2<-data.frame(y1,y2,y3,y4) df2
Output
y1 y2 y3 y4 1 2 6 3 2 2 0 2 4 1 3 1 1 7 3 4 1 1 2 3 5 0 4 2 0
Stacking data frame df2 −
Example
df2<-stack(df2) df2
Output
values ind 1 2 y1 2 0 y1 3 1 y1 4 1 y1 5 0 y1 6 6 y2 7 2 y2 8 1 y2 9 1 y2 10 4 y2 11 3 y3 12 4 y3 13 7 y3 14 2 y3 15 2 y3 16 2 y4 17 1 y4 18 3 y4 19 3 y4 20 0 y4
Example
z1<-rexp(5,1.02) z2<-rexp(5,1.02) z3<-rexp(5,1.02) z4<-rexp(5,1.02) df3<-data.frame(z1,z2,z3,z4) df3
Output
z1 z2 z3 z4 1 1.2908546 0.7256210 0.3485327 1.2388077 2 0.3096662 0.6603201 1.6009740 1.5944464 3 1.6638942 0.7771325 0.2083197 2.7376839 4 1.5370138 0.1080698 0.7180111 1.3909656 5 0.3302388 1.2617053 0.3907855 0.1516651
Stacking data frame df3 −
Example
df3<-stack(df3) df3
Output
values ind 1 1.2908546 z1 2 0.3096662 z1 3 1.6638942 z1 4 1.5370138 z1 5 0.3302388 z1 6 0.7256210 z2 7 0.6603201 z2 8 0.7771325 z2 9 0.1080698 z2 10 1.2617053 z2 11 0.3485327 z3 12 1.6009740 z3 13 0.2083197 z3 14 0.7180111 z3 15 0.3907855 z3 16 1.2388077 z4 17 1.5944464 z4 18 2.7376839 z4 19 1.3909656 z4 20 0.1516651 z4
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