Questions tagged [back-transformation]

Back transformation refers to efforts to reverse the effects of a transformation of one or more variables. Usually, the transformation has been done to meet assumptions of a model, but interest is in the original variable(s).

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363 views

How to untransform/interpret results after a Lambert W transformation?

Suppose I have some heavy-tailed data that I want to transform so it's roughly normal in order to perform a t-test. ...
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880 views

How do I estimate the prediction interval of back transformed log-normal data from Gaussian process?

I have some data that are clearly positively skewed and follow a log-normal distribution, lets assume the initial data is $Z = exp(Y)$, where $Y \sim N(\mu,\sigma^2)$. A Gaussian process assumes ...
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114 views

Mean and Standard Error of True Percentages (Not Binomial Proportions)

In my line of work I occasionally deal with data on the percent lipid of fish fillet (environmental sampling). The question came up today about how to calculate the mean and standard error and ...
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211 views

How to get the actual mean absolute error in cross validation after transforming the target variable y?

For a target variable y, it is transformed using np.log1p. Then a random forest regression model is trained using the ...
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65 views

How to recalculate Confidence interval after logarithmic and square transformations?

I'm performing test on one variance and in order to asses normality of X, I've transformed data with first natural logarithm transformation,then square transformation and calculated confidence ...
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216 views

Interpreting forecast predictions of log transformed data

Using the forecast function in R, I make a 1-step prediction for a log-transformed data set Y, ( Y = log(X) ). This prediction gives me a mean and a 95% prediction interval. How valid is this ...
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128 views

How to compute confidence intervals for a scaled reciprocal normal statistic

I have the following statistic of which I want to compute confidence intervals: \begin{equation} Z = \frac{(X-Y)^{-1}}{\mathbb{PVE}[(X-Y)^{-1}]}, \end{equation} where \begin{align} X &\sim\mathcal{...
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805 views

Back transforming reciprocal transformation for difference between means

Say I have the following datasets which concern normalised masses like this: Set 1: 3.08, 2.79, 3.62, 2.62, 2.85, 2.45, 2.80, 2.62 Set 2: 3.25, 3.14, 3.30, 3.13, 3.19, 3.17, 3.35, 3.35, 3.82, 3.13 ...
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315 views

Smearing estimate for cubic root transform in linear regression

I am building a cost model with cubic root transformation of the cost. Hence dependent variable is (cost)^(1/3). Now, am at a stage where i need to re-transform the predicted value to the actual cost. ...
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1answer
387 views

XGboost Regression Log Transform Target

I'm training a XGBoost Regressor to predict price which has a highly right skewed distribution. (all prices are positive) I took log transformation on the target thinking it would help to 1) stable ...
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35 views

Backtransform a log-odds transformation of the dependent variable in a Fixed Effects panel regression

I'm modeling a fixed effects (within) panel regression for a fractional dependent variable (DV) bounded between 0 and 1. My aim is to model the relationship so that I can predict the frational DV on ...
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1answer
20 views

Back-transformations

I have been having trouble grasping the idea of back-transforming data in R. Lets assume that I would like to perform an ANOVA on transformed data. I transform the response variable and all the ...
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180 views

Pairwise contrasts for logistic regression in emmeans, back-transform or not?

I ran a mixed effects logistic regression in R (glmer). The model identified a significant three-way interaction that I am interested in decomposing using post-hoc multiple comparison in emmeans. In ...
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28 views

predicting waste per capita: is a Gaussian model correct?

I am trying to predict the daily amount of waste per person produced in the fishery sector. We surveyed fishing boats at the end of their fishing trip and the variables I have are duration of trip (...
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66 views

Back-transforming forecast points and error bounds from a VAR model applied to alr-transformed compositional time series

The data I have a k=3 compositional time series from which I am trying to forecast future values. The series is compositional in that at each time ...
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46 views

How do I back-transfrom my estimates (and confidence intervals) from log10 variables (both independent and dependent) in linear model

I ran linear models for a bunch of variables in R. Both variables are log10 transformed (dependent and independent). I already took a look in some online documents and videos about this but i guess I'...
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115 views

How to plot estimate + raw data of a Bayesian zero inflated poisson?

GENERAL QUESTION: How to back-transform estimates from a zero-inflated poisson to obtain the original scale in R? (I tried exponential like for poisson but the results are wrong) DETAILED ...
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928 views

Back transforming GLM standard errors

This is a very simple question. When I back transform log transformed coefficients it usually looks like this: exp(interceptvalue) + exp(paramter1 coefficicent) ...
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430 views

Back-transforming Log data from a paired t.test (R)

I am working with this data set: ...
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84 views

How to explain results from a graph of a variable transformed with exponential function?

I had to transform my response variable before my analysis, but the only transformation that worked well was the exponential. So, I could not back-transform my values to the original scale. How do I ...
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267 views

How do I back transform predicted values when multiple transformations are present in multiple regression?

Suppose two predictors are desired for a multiple linear regression. Upon reviewing scatter plots, the first requires a power transformation, log(y)= b0 + b1log(x), and thus the back transformation of ...
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87 views

Question regarding back transformation of data

I have a data set that boils down to accuracy levels in a response task. In order to run an ANOVA on the accuracy data I've been advised to perform a arcsine square root transform on the data first. ...
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68 views

Detect grid in 2D plane

Given is a set of points (x,y) in a two dimensional Cartesian coordinate system. Many points are near the crossing points of an affine transformed grid. The points have been measured and may have: ...
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98 views

Plotting data and polynomial equation when x-values have been transformed

I hope I can make my question clear, if not I will be happy to clarify. I want to present a simple regression plot with the polynomial equation line linked to it. Those data have been tested in a ...
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16 views

metrics of backtransform from logit-normal

Suppose I generate iid random data, logit-normal, where the mean (0.8472979) corresponds to mu=0.7 on the back-transformed probability scale (i.e., expit(0.8472979)=0.7). SD of the iid sample on the ...
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14 views

Back-transformation in pairs function (lmer analysis)

I'm running lme4 and Im working with a dataset where the variables a,d,e are logtransformed. I wonder how to handle back-transformation concerning the "pairs" function. How do I get the ...
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11 views

Transforming log-scaled splines regression outputs to an understandable scale

Please give me some advice. I am using brms package and mgcv package for two regression models: bernoulli lognormal The problem is that both of these models outputs are in lognormal scale. As much ...
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8 views

Do I need to backtransform the estimates of a model produced with the mhurdle package using box-cox normal distribution?

I am currently running a double hurdle model with the R command "mhurdle". My data is not normally distributed and I am using the box cox normal distribution on because that yields the ...
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14 views

Can we transform back calendar adjusted forecast?

I've monthly data, I adjusted it for monthdays and conducted a forecast. After that can I adjust it back and compare it with untransformed time serie?
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58 views

Back-transformation of coefficients in a log-log model, and a model with a boxcox transformed y

There's a number of posts out there on back-transformations but none that I've been able to use to answer this problem, internet searches are returning surprisingly little on the issue of back-...
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16 views

Interpreting differences in log-transformed data when constant has been added first

I have performed an ANOVA on some log-transformed data. I had planned to transform the mean differences in the log-transformed data back to the original scale and interpret them as ratios of the ...
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24 views

What is the back-transformation of Log((Max Y + 1) - Y)?

I have performed a linear mixed model regression with the transformation on the outcome variable, Y, Log((Max Y + 1) - Y). This gives normally distributed residuals when simpler transformations did ...
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19 views

Transformation of Beta distribution prior parameters for group testing analysis

As described here Optimization of pool size and number of tests for prevalence estimation via group testing I'm trying to estimate the prevalence of a lab test in a population (PCR for COVID-19) ...
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29 views

Back-transforming coefficients of glmer model fit using rescaled independent variables for prediction & plotting

I've fit a model using the glmer function from the lme4 package. Because my predictor variables are on very different scales, I ...
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88 views

Unmarked OccuMulti function

I have a question about the occuMulti function in the package “unmarked”. I have fitted the following model for a two-species interaction between puma and peccary: ...
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1answer
74 views

Which one is correct presentation for descriptive statistic of a transformed variable between retransformed mean (estimated SD), and median (qurtiles)

If a collected variable has a skewed distribution toward one side and transformed for statistical analysis, which one is better for descriptive statistics presentation between re-transformed mean and ...
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74 views

Why are the confidence intervals so large for the difference of differences?

I have run a generalized linear mixed effects model with the glmmTMB package to determine if there is an interaction between two categorical predictors, treatment and location, in predicting the ...
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152 views

Back transforming the intercept of double log normal distribution

I apologise if this is a duplicate, i couldn't find a thread that seem to be talking about the same thing. I have a dataset with a bunch of duration of varying lengths in seconds, i log-transformed ...
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297 views

Back-Transformation for Ln(X+1) of zero rich data

I have seen and read several similar questions, but mine pertains specifically to zero rich data. I will be back transforming my data based on a first order Taylor series approximation. As outlined ...
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1answer
39 views

Log transformed data

When you log transform data what is being tested on the original scale of the data? And why can we use our log transformed data to answer our scientific question? We are looking at data comparing ...
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1answer
170 views

Transforming non-normal to normal distribution and back-transform

I would like to transform non-normal distribution to normal distribution, and back-transform to its original state (or at least close to the original state). From this article, I've read that you can ...
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75 views

Interpret Quadratic Regression with Asinh transformation

I have a regression equation that uses covariates of the following form asinh(y) = b0 + b1 asinh(x) + b2 (asinh(x))^2 + error and am wondering how to intepret the ...
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440 views

Box-Cox Transformation on Single Variable and Interpretation of the Transformed Variable's Mean and Standard Deviation

I'm revisiting the Box-Cox transformation in one of my stats books, and I started playing around with the SAS macro %BCTRANS2 (Source: http://support.sas.com/resources/papers/proceedings12/430-2012....
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44 views

95% CI interpretation on transformed data using (abs(x-mean(x)))

I have a problem for which no search has provided an answer. I am using lm() to build a model which I tested to ensure it met all assumptions using the following <...
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296 views

Interpreting log transformed linear regression

I have created a linear regression model using log transformed data but I'm having issues interpreting the results. The r^2 of the model is .67 but I'm not sure what else I can report. I guess ...
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540 views

AIC in R: Back-transformation of model averaged coefficient estimates

I am running an analysis using a mixed model with lmer in R. I am using AIC as my model selection process. I have a global model and am including within the selection process all subset models ...
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150 views

Rewriting linear equation

So I have a linear equation produced in R: logBodyWt = -1.08968 + 1.22496 x logBrainWt And that's all groovy but there is a question in a module which asks me to "Rewrite your model as a non-linear ...
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217 views

Back transforming a constant for geometric mean

I have a series of non-normal variables that include negative values. I have transformed the data by adding a constant of +10 to each variable (the lowest value was close to -9) and then log ...
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3k views

Can I normalize a data proportion?

Is there any way to normalize this variable (attached)? In fact, this is a proportional data (a percentage). But I need transform it in order to do some contrasts. I try with arcsine transformation: 2 ...