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Server Side Programming Articles
Page 1149 of 2109
How to check whether a column exists in an R data frame?
If we have very large data set then it is highly that we forget the column names, therefore, we might want to check whether a particular column exists in the data frame or not if we know the column name. For this purpose, we can use grep function that will result the column name if exists in the data frame otherwise 0. To understand how it works check out the below examples.Example1ID
Read MoreHow to find the sum of squared deviations for an R data frame column?
The sum of squared deviations is the total of the square of difference between each value and the mean. To find this value, we need to create the formula in R platform. For example, if we have a data frame called df that contains a column x then the sum of squared deviations for x can be calculated by using sum((df$x−mean(df$x))^2).Example1y1
Read MoreHow to find the correlation of one variable with all the other variables in R?
To find the correlation of each variable with remaining variables, we can create a correlation matrix but for the correlation of only one variable with all the other variables we need to define the columns inside the cor function. The output will represent the columns and rows as passed inside the function.Example1y1
Read MoreHow to create a column with largest size string value in rows in an R data frame?
To create a column with largest size string value in rows, we can use apply function and define the size of the string for the largest value by creating a function as shown in the below examples. If the number of characters in all the columns are same or there exists some ties then the output will be the first one.Example1y1
Read MoreHow to use column index instead of column name while using group_by of dplyr in R?
When we use group_by function of dplyr package, we need to pass the column name(s) that are categorical in nature. If we want to use the index of the same column(s) then group_by_at function needs to be used, where we can pass the column index as the argument.Example1y1
Read MoreHow to check if a list element is greater than a certain value in R?
If we have a list that contains numeric elements and we want to check whether the elements are greater than a certain value then as.numeric function can be used. The output of the function will be in 0/1 format where 0 represents FALSE and 1 represents TRUE. For example, if we have a list called LIST then to check whether elements in LIST are greater than 2 can be done as as.numeric(LIST>2).Example1List15)Output[1] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0 0Example2List22)Output[1] 1 1 1 1 0 0 1 0 1 1 1 1 1 0 0 0 1 1 1 0
Read MoreHow to find unique matrices in a list in R?
A list can contain many types of elements such as vectors, matrices, data frames etc. If we have matrices in a list then to find unique matrices in that list, we can simply use unique function. For example, if we have a list called LIST that contains matrices having some duplicate matrices then unique matrices can be extracted by using unique(LIST).Example1list(M1=matrix(1:25, ncol=5), M2=matrix(1:25, ncol=5), M3=matrix(1:25, ncol=5), M4=matrix(rpois(25, 5), ncol=5)) List1Output$M1 [, 1] [, 2] [, 3] [, 4] [, 5] [1, ] 1 6 11 16 21 [2, ] 2 7 12 17 22 [3, ] 3 8 13 18 ...
Read MoreHow to find mean and standard deviation from frequency table in R?
To find the mean and standard deviation from frequency table, we would need to apply the formula for mean and standard deviation for frequency data. For example, if we have a data frame called df that contains a column x for units and frequency for counts then the mean and standard deviation can be calculated as −Mean = sum(df$x*df$frequency)/sum(df$frequency) SD = sqrt(sum((df$x−Mean)**2*df$frequency)/(sum(df$frequency)−1)) respectively.Example1x
Read MoreHow to export data frame in R to excel?
To export data frame in R to excel can be done with the help of write.xlsx function of xlsx package. We would need to pass the data frame name, the file name and the sheet name in which we want to save the data frame. For example, if we have a data frame called df with file name Excel_df and on sheet1 then the data frame will be saved by using the below command −write.xlsx(df, file="Excel_df.xlsx", sheetName = "Sheet1")Consider the below data frame −Examplex
Read MoreHow to plot matrix columns as lines in base R?
To plot matrix columns as lines in base R, we can use matplot function but we need to read the matrix as a data frame using as.data.frame function and for creating lines the type argument will be used. For example, if we have a matrix called M then the columns of M can be plotted as lines using the command matplot(as.data.frame(M),type="l").Consider the below data frame −ExampleM
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