Linked Questions

-1
votes
1answer
2k views

log transformation - negative values [duplicate]

I am trying to log transform time series data of Inflation. However, there is one negative value. I have added the constant 1 to all my values and the log transformed. ...
1
vote
0answers
844 views

Log transform with 'zero' values [duplicate]

I am doing some explorative work on two large datasets. One from 2001 and one from 2018. The dataset consists of measured soil-parameters and it contains lots of zero's. From the transformations ...
0
votes
0answers
57 views

Is it good practice to add 1 to 0 scores in log-normalization? [duplicate]

I am apply log-normalization to my non-normal data. However, when I apply log-normalization, the 0 values is converted into inf, which makes it impossible to apply ...
0
votes
1answer
49 views

Resolving skew and determining the back transformation function [duplicate]

I have a skew variable and I want to use box-cox transformation (log) but around 50 observation out of 200 are between 0 and 1. My initial thought was to add a constant to all observations before ...
255
votes
150answers
134k views

Famous statistical quotations

What is your favorite statistical quote? This is community wiki, so please one quote per answer.
199
votes
12answers
147k views

How should I transform non-negative data including zeros?

If I have highly skewed positive data I often take logs. But what should I do with highly skewed non-negative data that include zeros? I have seen two transformations used: $\log(x+1)$ which has the ...
33
votes
7answers
13k views

Combining probabilities/information from different sources

Lets say I have three independent sources and each of them make predictions for the weather tomorrow. The first one says that the probability of rain tomorrow is 0, then the second one says that the ...
47
votes
4answers
27k views

Regression for an outcome (ratio or fraction) between 0 and 1

I am thinking of building a model predicting a ratio $a/b$, where $a \le b$ and $a > 0$ and $b > 0$. So, the ratio would be between $0$ and $1$. I could use linear regression, although it doesn'...
46
votes
1answer
35k views

Regression: Transforming Variables

When transforming variables, do you have to use all of the same transformation? For example, can I pick and choose differently transformed variables, as in: Let, $x_1,x_2,x_3$ be age, length of ...
6
votes
3answers
3k views

How to interpret this QQ plot?

I have ran a QQ plot on R on my data using par(mfrow=c(1,2)) par(pty="s") qqnorm(TEDS$LST1); qqline(TEDS$LST1) which gave me this: The histogram of the data ...
11
votes
2answers
10k views

Distribution for percentage data

I have a question about the correct distribution to use for creating a model with my data. I conducted a forest inventory with 50 plots, each plot measures 20m × 50m. For each plot, I estimated the ...
5
votes
2answers
15k views

How to log transform data with a large number of zeros

I have a dataset comprised of continuous values that have about 30-50% zeros and a large range (10^3 - 10^10). I believe these zeros are not a result of missing data and are the result of the ...
5
votes
2answers
567 views

Alternatives to multilevel model with log transformed outcome

I'm working with linear mixed-effects model in Stata. Dataset has three levels of 100k observations, nested in 500 regions, nested in 70 regions. Currently my modelling strategy is to use three-...
4
votes
2answers
2k views

How to interpret a log transformed (X+1)?

Assume that I have a log transformed model as follows: Model 1: $Y = a + b\ln(X)$. Interpretation: a 1% increase in $X$ is associated with an average $b/100$ units increase in $Y$. If I add $1$ to $...
-2
votes
1answer
6k views

How to perform boxcox transformation on data in R tool [duplicate]

Possible Duplicate: How should I transform non-negative data including zeros? Error in boxcox.default(y ~ x) : response variable must be positive I want to perform box cox transformation on ...

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