How to do log transformation in R-Complete Guide

How to do log transformation in R?, when working with statistics, it occasionally happens that data become skewed, with higher concentrations at one end and lower values at the other.

As a result, there is a peak at one end that gradually declines. Using a logarithmic scale to give this type of data a more regular pattern is one method to handle it.

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To alter the dependent and independent variables and correct for any skewed data that can interfere with your linear regression, arcsine transformation, geometric mean, negative value, or other linear relationship in your original data, utilize logarithmic transformation.

You can improve the normality assumption for your original data distribution by applying a logarithmic transformation, which makes it simpler for a linear model to complete any statistical test using modified data.

Log in R

The log() function, which returns the logarithm of the value in the base and has the formatted log(value, base), is the fundamental method for performing a log in R.

This function generates a natural logarithm of the value by default. This will assist remove any skewness from your data distribution and turning it into a numeric variable regression model that more closely resembles normal arithmetic mean for the purposes of regression analysis and scatter plots.

Although this particular data transformation technique is not the most straightforward, it produces some of the best results for the response variable and log-transformed data of any other linear transformation that is comparable, such as a logit transformation, square root transformation, arcsine transformation, reciprocal transformation, or inverse transformation.

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Base 2 and base 10 each have different shortcuts.

log(16,4)
[1] 2

With 16 as the value and 4 as the base, this is the fundamental logarithm function. Since 16 is the square of 4, the outcomes are 2.

log(10)
[1] 2.302585

The base of e is used to get the natural logarithm of 10 in this case because the second perimeter has been removed.

log(1000,10)
[1] 3
log10(100)
[1] 3

Here, we have a comparison of the base 10 logarithms of 1000 obtained by the basic logarithm function and by its shortcut. For both cases, the answer is 3 because 1000 is 100 squared.

Base notation

log(16,2)
[1] 4
log2(16)
[1] 4

Here, we compare how the basic logarithm function and its shortcut compute the base-2 logarithm of 16. Since 16 = 2 cubed, the answer in both situations is 4.

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Log transformation

Data is subjected to a log transformation in order to lessen its skew. This is typically done when the data is severely skewed in order to lessen the skew and make the data easier to understand.

Applying the log() function on a vector, data frame, or other data set in R results in a log transformation.

To avoid applying a logarithm to a 0 number, 1 is added to the base value prior to applying the logarithm.

The data is presented in a less skewed manner as a result, making it simpler to comprehend.

vectors

Doing a log transformation in R on vectors is a simple matter of adding 1 to the vector and then applying the log() function. The result is a new vector that is less skewed than the original.

vector transformation

vect<-c(200,20,50,2,1,0.5,0.1,0.05,0.01,0.001,0.0001)
log(vect+1)
1] 5.3033049081 3.0445224377 3.9318256327 1.0986122887 0.6931471806 0.4054651081
[7] 0.0953101798 0.0487901642 0.0099503309 0.0009995003 0.0000999950
plot(vect)
plot(log(vect+1))

The statistics above demonstrate that vect is more skewed than log (vect+1). The graphs generated by the two plot functions using this code make this truth more clear.

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Data Frame

A data frame makes log transformation a little more challenging because separating the data is necessary to obtain the log.

You can obtain the log of each data point by taking the log of the entire dataset. However, you typically just require the log from a single data column.

Data frame column

ChickWeight$logweight<-log(ChickWeight$weight)
head(ChickWeight)
   weight Time Chick Diet logweight
1     42    0     1    1  3.737670
2     51    2     1    1  3.931826
3     59    4     1    1  4.077537
4     64    6     1    1  4.158883
5     76    8     1    1  4.330733
6     93   10     1    1  4.532599
plot(head(ChickWeight$Time),head(ChickWeight$logweight))
plot(head(ChickWeight$Time),head(ChickWeight$weight))

As you can see, the syntax for gaining access to the data in each particular column is dataframe$column.

The default value of the head() function is 6, and it returns a specified number of rows from the start of a data frame.

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To demonstrate the impact a log transformation makes these plot functions graph weight vs. time and log weight vs. time.

While log functions themselves have a wide range of applications, they may also be used in data science to arrange data display into a clear pattern.

They come to be handy for minimizing data skew so that more detail can be viewed. They can be used with R on a variety of data types, including simple numbers, vectors, and even data frames.

Another benefit of using R as a data science tool is the utility of the log function.

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