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R Programming Articles
Page 36 of 174
How to find the sum of values based on key in other column of an R data frame?
If we have a column that is key that means we want to use that column as an independent variable and find the statistical values such as sum, mean, standard deviation, range, etc. for the dependent variable. This can be done with the combination of with and tapply function as shown in the below examples.Consider the below data frame −Examplex1
Read MoreHow to find the length of the largest string in an R data frame column?
The length of the largest string can be found with the help of max function combined with nchar function. For this purpose, we first need to access the appropriate column that contains string values. Suppose, we have a data frame called df that contains a string column defined as CHAR then the length of the largest string will be found by using the command max(nchar(df$CHAR)).Consider the below data frame −Examplex
Read MoreHow to find the first quartile for a data frame column in R?
The first quartile is the value that exists at the 25th percentile, that means there are 25% of values in the data that lie below first quartile. When we find the summary of data frame the output returns this value but if we want to extract only the first quartile then quantile function can be used by specifying the percentage using 0.25.Consider the below data frame −Examplex
Read MoreHow to create boxplot using ggplot2 without whiskers in R?
To create boxplot using ggplot2 without whiskers, we need to use coef argument inside geom_boxplot function. For example, if we have data frame called df and there exists one categorical variable x and one response variable y then the boxplots for categories without whiskers can be created by using ggplot(df,aes(x,y))+geom_boxplot(coef=0).Consider the below data frame −Examplex
Read MoreHow to display 0 at Y-axis using ggplot2 in R?
To display 0 at Y-axis, we can set the limits for Y-axis using scale_y_continuous function of ggplot2 package. For example, if we have two columns say x and y in an R data frame called df then the scatterplot with displaying 0 at Y-axis can be created by using the below commandggplot(df,aes(x,y))+geom_point()+scale_y_continuous(limits=c(0,”upperlimit”))Consider the below data frame −Examplex
Read MoreHow to create a sequence of values between two vectors in R using corresponding elements?
If we have two vectors say x and y, x contains 1, 6 and y contains 5,10 then the sequence of values between these two vectors will be 1, 2, 3, 4, 5 and 6, 7, 8, 9, 10. Here the sequence is created by using the corresponding elements in x and y. To do this in R, we can use mapply function as shown in the below examples.Examplex1
Read MoreHow to check if two matrices are equal in R?
When we matrices of larger size and the data is expected to from the same distribution or from same sources then we might expect that the matrices are equal. In this type of situations, we would like to check whether the two matrices are equal or not. This can be done with the help of all.equal function as shown in the below examples.ExampleM1
Read MoreHow to sort an R data frame column without losing row names?
When we sort a data frame column in R, the row names are lost but we might need them. Therefore, sorting without losing row names is required and it can be done with the help of order function. For example, if we have a data frame called df that has a column x then sorting of x without losing row names can be done by using the below command −df[order(df$x),,drop=FALSE]Consider the below data frame −Examplex1
Read MoreHow to find the column index in an R data frame that matches a condition?
To find the column index that matches a condition, we can use apply function. This condition could be values in columns greater than something, less than something, equal to something, or any other condition for numerical variables. For example, if we want to check which columns of data df contains value in rows greater than 5 then we can use the command apply(df,1, function(x) which(x>5)).Consider the below data frame −Examplex1
Read MoreHow to extract first value from a list in R?
To extract first value from a list, we first need to access the element using double square brackets then the sub-element of each element will be accessed using single square brackets. For example, if we have a list called LIST containing five elements each having 10 elements then the first sub-element of the LIST will be selected by using LIST[[1]][1].ExampleList1
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