The logarithm of a number is the power to which the base must be raised to get the number.

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27 views

Is there a model with additive effects for always positive dependant variable?

When modeling a dependant variable always positive and continuous, models as log-transformed linear model or GLM with log link are generally used. The log-transformed linear model is : ...
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9 views

If you transform response time data, e.g. to generate a CI, do you transform the values back for interpretation? [duplicate]

I would like to create a CI or highest density interval for response time data. The distribution of the response times is quite skewed and I think about transforming them by LN(y). However, my ...
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1answer
20 views

Normality test on logarithmic data

I had to take the log of my data, and now I want to test for normality of my data. Can I use the standard normality tests or do I have to use some special test? I used the ...
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33 views

Back-transform coefficient from linear mixed model with log-transformed response

I ran a linear mixed model (lme4::lmer in R) with a log-transformed (base 2) response, and predictors were not transformed. I want to back-transform my coefficients to make a statement about effect ...
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40 views

Curve Fit with logarithmic Regression in Python

I need to find a model which best fits my data. It's look like this: So I thought about logarithmic regression. But when I try to make a simple fit in python I get the following result: My code ...
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6 views

Multiplicative Measurement Error in Response Variable

I understand that taking log of the multiplicative error model transforms it into the additive error model. Let $y'$ be the observed response variable, with $y$ being the true response variable and ...
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1answer
31 views

Log-transforming time series data before cointegration testing

I am testing the cointegration between these variables: Gold Price (Ringgit), Exchange Rate - MYR to USD (Ringgit), Real Effective FX Rate Based on CPI, T-Bill 10 Years Rate, Consumer Price Index. ...
3
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1answer
48 views

log-log transformation

I am making a linear regression model for house prices. My data set includes price per square foot of a property and floorspace so I have multiplied them to get the total price of each property. My ...
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1answer
19 views

Exponential Regression with x outside of exponential

I am trying to do exponential regression by matrix notation, and I am trying to figure out to create my $\mathbf{X}$ matrix to fit my model. I know that I need to use a model function of the form $c_1 ...
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1answer
26 views

Running Same Regression Across Multiple Individuals

I am trying to run a log log regression of the form LNX ~ LNP, where X = Units Sold and P = Price (in reality, I would have a number of other variables included in the model). The data is retail ...
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24 views

Alternative scaling methods to log

I have data (as below). When I plot, the details of 0-10 are lost. So I scale it using a log function and then it seems that detail is lost throughout. Is there another scaling method that would work ...
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16 views

Normalizing logarithmic data in a range from 0 to 1

i am replicating a multilevel-analysis for my bachelor thesis (with newer data + corrections). The author i am citing used the unstandardized coefficients of every independent variable as beta ...
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1answer
24 views

data transformation in regression

I am going through a research paper on HbA1C (hemoglobin) management of diabetic patients. The author has used multilevel model as it has repeated measures. The DV has been log transformed. To ...
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0answers
19 views

Transforming Log Values in Predicted Values (Low Predicted Scores)

I have a problem with the logging of a price variable. The logging of the variable helps the model performance considerably. The value is positively skewed so this makes sense mathematically. I run ...
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2answers
28 views

How do I correctly compare bacterial counts from mice with different genotypes?

As far as I know, CFU counts from bacterial suspensions should approximately follow a Poisson distribution. So in order to perform a One-way Anova, a mathematical transformation to achieve normality ...
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1answer
52 views
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17 views

Nonparametric estimation of the logarithm of a density

I was wondering whether there is an equivalent to Kernel Density Estimation to estimate nonparametrically the logarithm of a density. Or if there is any nonparametric method for that. (Taking the ...
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0answers
61 views

Do we need to log-transform a variable that already is in percentage form?

I came across this website while searching for knowledge and help in statistics. As far as I know, we log-transform variable in order to avoid the heteroskedasticity problem. However, if any of the IV ...
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32 views

Minimizing RMSE while using a log-transformation

I am trying to fit a linear model to some data, but the dependent variable y is clearly not normally distributed. It has a heavy tail on the right. A log-transformation helps to make the ...
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1answer
34 views

Store logarithm of a variable in data set

I have seen many data sets where some of the variables are listed both with their original value and the logarithm of the variable. For instance, a data set could have the variables ...
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77 views

How to perform logarithmic binning

I'm trying to program (in C++ if relevant) some functionality to plot a histogram that does logarithmic binning. The range of values run from 0 to M (there is a possibility for negatives but we're not ...
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0answers
10 views

Re-arranging log-linear equation to get slope on standard (not logarithmic) scale [duplicate]

The equation for log-linear regression is: logY = mx+c [eq 1] therefore: (logY-c)/x = m [eq 2] And to get slope on standard scale we can do: exp((logY-c)/x) = exp(m) [eq 3] but Im ...
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38 views

Coefficient in differences-in-differences regression significant for log-level specification but not for level level

I am estimating a differences in differences model: $Y_{it} = \alpha_i + \beta_t + \tau T_iP_t + \epsilon_{it}$ where $\alpha_i$ and $\beta_t$ are fixed effects, $T_i$ is a dummy variable indicating ...
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35 views

Correction for logarithmic bias

I fitted the variable that has been log transformed (log(y + 1)) by means of mixed model. I used lme function from ...
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1answer
34 views

multiplying an outcome and predictor values by ten flips the sign of an effect size when log transformed. WHY?

I have a model, y~ x1 + x2 + x1*x2, where y and x1 are strongly correlated and ...
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0answers
18 views

How to use ln-transformation with loads of zeroes?

I came across a method of ln-transforming exogenous variables in non-negative data sets with loads of zeroes in a lecture. With the method proposed, one simply ln-transforms the variable in question ...
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1answer
103 views

Is there something clever I can do with a log of a sum?

In something I'm working on, the expression $$\lim_{n\rightarrow\infty}\exp\left(-\frac{1}{n}\log\left(\prod_{i=1}^{n}X_{i}+\prod_{i=1}^{n}Y_{i}\right)\right)$$ came up, in which all $X_{i}$ $iid$ and ...
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2answers
78 views

How do I change logarithmic scaled data to linear scaled data?

I am using decibels for my research, and I was told by someone that I cannot perform any statistical analyses on these measurements other than basic descriptive statistics because the data are ...
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1answer
231 views

How can I recognize when I must apply “log transformation”?

I have some time series - http://ww2.coastal.edu/kingw/statistics/R-tutorials/simplenonlinear.html In this article author try to use log transformation for pressure data. How can I recognize that ...
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0answers
48 views

How to interpret log-transformed predictors in probit regression?

I am running a probit model with several continous and one log-transformed predictor (firm size as total assets). I am unsure how to interpret the coefficient of -0.341 on that variable. I used the ...
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1answer
268 views

Back transformation of log10 transformed data in SPSS

I have transformed my quantitative variable by using the log10 function in order to run some parametric tests (ANOVA) but when I want to make pairwise comparisons ...
2
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1answer
63 views

What is the difference between a $\log_{10}$ and logit transformation?

What is the difference between a $\log_{10}$ and logit transformation? I have tried to find the answer elsewhere but cannot find a strict distinction.
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1answer
147 views

Why don't log-likelihoods lead to log(0)?

How do log likelihoods function in practice? I seem to oscillate between understanding this and not understanding this (which most likely means I've never understood it). When you take log( P( X | Y ...
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0answers
13 views

Variance of the logarithm of a binomial distributed random variable

What is the variance of $\log(1+X)$, where $X \sim Bin(n,p)$. I am looking for an approximate solutions depending on n and p. I have tried Taylor expanding the logarithm, but it didn't lead to a ...
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1answer
91 views

Rule of thumb for using logarithmic scale

When I am given a variable, I usually decide wether to take its logarithm based on gut feeling. Usually I base it on its distribution - if it has long tail (like: salaries, GDP, ...) I use logarithm. ...
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1answer
26 views

goodness of fit log transformed vs not log transformed

I have a relationship of two variables which is somehow log shaped. Now, I establish two models for this dataset, for one I log transform the dependent variable: ...
2
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1answer
104 views

log-log vs. normal plotting for showing linear dependency

I have a set of data, basically measuring the running time of an algorithm against some gathered input. This is the summary of data: ...
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1answer
154 views

GLMM with Gamma distribution vs. Gaussian distribution with log transformation

Is there really a difference in result if I use a GLMM with Gamma distribution vs. a model with a Gaussian distribution with log transformation? If so, how do I choose between the two methods? See ...
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1answer
43 views

transforming exchange rate and inflation rate

I am testing some variables in percentage (exchange rate, inflation, and GDP growth rate), and I am a bit hesitate whether it is better leave them as percentage or transform them into log values. ...
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1answer
162 views

Interpretation of log(1 + x) transformed predictor

Interpretation of log transformed predictor neatly explains how to interpret a log transformed predictor in OLS. Does the interpretation change if there are 0s in ...
3
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1answer
75 views

Large Increase in Naive Bayes Accuracy results in decrease precision?

I am trying to classify (37 possible classes) a dataset that has 9 features and 900,000 occurrences. I have tried a couple different algorithms but the one that gave the lowest logarithmic loss was ...
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1answer
85 views

Log linear model interpretation - % Contributions?

I know that for log-lin models the interpretation for the coefficiente is this one, that is: Coefficients⋅100 have a semi-elasticity interpretation: for a 1 unit change in x, you get b*100% change in ...
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1answer
1k views

How to transform negative values to logarithms?

I would like to know how to transform negative values to Log(), since I have heteroskedastic data. I read that it works with the formula ...
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1answer
158 views

Should I use the mean difference or mean ratio for a t-test?

I have a quantitative variable (medication dose) that is paired: dose of medication before surgery and after surgery for 76 patients. I was under the impression that I should calculate the mean of ...
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0answers
183 views

How to backtransform data that has been log transformed in order to report raw values for ease of interpretation?

I have run some lme4 analyses on reaction time data in R, with RT being the main outcome variable of interest, which I first log transformed due to non-normality ...
0
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0answers
23 views

Natural logarithm transfomation and zeroes [duplicate]

I am using Stata 13 to estimate a simple regression. Given a rather positive skew of a few of my covariates, I figured to ln-transform the variables. However, I have a substantial amount of zeroes in ...
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82 views

How to treat missing values in a regression?

I have used the logarithmic form of wage as my independent variable in Stata. However, it contains missing values. Should I replace these with 0 or let them be?
4
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1answer
138 views

Log Transformation

I am planning to run a 2x2x3 repeated measures ANOVA on reaction time data pre and post treatment. However, my data is skewed and I wanted to do a log transformation but have few questions. Can I ...
0
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0answers
13 views

Meaning of growth of log-transformed variables [duplicate]

I am dealing with the transformation of the variables for my master thesis (a panel dataset with a xtabond2 model). The analysis focuses on growth rates, so my co-director told me to transform the ...
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182 views

Cohen's D: Should I use raw data, log transformed data or back transformed data?

I am a doctor and right now I am doing medical research. I have some questions about cohen's d. I try to research it on the internet but it seems there is not much answer to this question. My project ...