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Server Side Programming Articles
Page 1239 of 2109
How to find the indexes of minimum values in a vector if there are ties in R?
If we have repeated values in a vector that means we have ties in the vector, therefore, the indexes of values will help us to identify the positions of a particular value in the vector. We can use which function with min function to find the positions of minimum values in a vector, if there exists more than one minimum then the output will show all the relevant positions.Examplex1
Read MoreHow to select only one column from an R data frame and return it as a data frame instead of vector?
Generally, if we extract a single column from an R data frame then it is extracted as a vector but we might want it in data frame form so that we can apply operations of a data frame on it. Therefore, we can use single square brackets for the extraction with T (TRUE) or (FALSE) values and drop = FALSE so that the output becomes a data frame.Consider the below data frame −Exampleset.seed(999) x1
Read MoreHow to calculate population variance in R?
There is no function in R to calculate the population variance but we can use the population size and sample variance to find it. We know that the divisor in population variance is the population size and if we multiply the output of var(it calculates sample variance) function with (population size – 1)/population size then the output will be population variance.Exampleset.seed(141) x1
Read MoreHow to save an R data frame as txt file?
If we want to use a data frame created in R in the future then it is better to save that data frame as txt file because it is obvious that data creation takes time. This can be done by using write.table function. For example, if we have a data frame df then we can save it as txt file by using the code write.table(df,"df.txt",sep="\t",row.names=FALSE)Consider the below data frame −Exampleset.seed(111) x1
Read MoreHow to create a subset of an R data frame having complete cases of a particular column?
If we have missing values in a data frame then all the values cannot be considered complete cases and we might want to extract only values that are complete. We might want extract the complete cases for a particular column only. Therefore, we can use negation of is.na for the column of the data frame that we want to subset.Consider the below data frame −Exampleset.seed(123) x
Read MoreHow to fill the NA with last observation in the column of an R data frame?
There are multiple ways to fill missing values in data analysis and one of the ways is filling them with the previous value in the same column of the data frame. For example, if we have a column x in data frame df and this columns x contains some NA values then we can fill them with the values in the upper row. This can be done with the help of na.locf function of zoo package.Consider the below data frame −Exampleset.seed(477) x
Read MoreHow to find the root mean square of a vector in R?
To find the root mean square of a vector we can find the mean of the squared values then take the square root of the resulting vector. This can be done in a single and very short line of code. For example, if we have a vector x and we want to find the root mean square of this vector then it can be done as sqrt(mean(x^2)).Examplex1
Read MoreHow to round correlation values in the correlation matrix to zero decimal places in R?
To find the correlation matrix, we simply need to use cor function with the data frame object name. For example, if we have a data frame named as df then the correlation matrix can be found by using cor(df). But the result will have too many decimal places to represent the correlation. If we want to avoid the values after decimal places, we can use round function.Consider the mtcars data in base R −Exampledata(mtcars) cor(mtcars)Output mpg cyl disp hp drat ...
Read MoreHow to change a data frame with comma separated values in columns to multiple columns in R?
Mostly, we need to import the data from an outside source in R environment for analysis and these data can be recorded as comma separated values that represent rows. If we want to create the columns for the comma separated values then cSplit function of splitstackshape package can be used. In the below example, we have created a data frame with comma separated values then splitting those values as single value in each column.Consider the below data frame −Exampledf=data.frame(x=apply(matrix(rpois(200, 10), 20, 10), 1, paste, collapse=", ")) dfoutputx 1 8, 12, 7, 12, 10, 8, 11, 6, 8, 7 2 9, ...
Read MoreHow to create a subset of a matrix in R using row names?
When we create a matrix in R, the row names and column names are not defined but we can define them separately. If we want to take a subset of rows of a matrix then row numbers can be used within single square brackets but if we want to do it with the names then we need to specify those names.ExampleM1
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