Mathematical re-expression, often nonlinear, of data values. Data are often transformed either to meet the assumptions of a statistical model or to make the results of an analysis more interpretable.

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3 views

Johnson transformation in Minitab allows a too narrow data range

I am using Individual Distribution Identification in Minitab 16, to identify the distribution of 19 values. The Johnson transformation is the only decent fit, and the equation I get is the following: ...
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13 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
17 views

Standard error of Weibull distribution parameter estimates

Hi I am new to R and I am trying to fit a Weibull distribution to my data. I see that the data has the following characteristics. To me it appears that the standard error of the scale parameter is ...
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25 views

How to assess variable to transform in multiple regression?

I have a multiple regression model and when I check its residuals vs fitted I have determined a transformation of some kind needs to take place ... but I don't know which variable to start with (4 ...
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10 views

How do I remove the header names in a vector? [on hold]

I have a character vector which looks like this: ` NA1 NA2 NA1 NA2 NA1 NA2 "4e" "41" "4e" "41" "4e" "41" ` I want to remove the NA1,NA2,.... headers ...
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1answer
22 views

centering and scaling dummy variables

I have a data set that contains both categorical variables and continuous variables. I was advised to transform the categorical variables as binary variables for each level (ie, A_level1:{0,1}, ...
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1answer
16 views

How to connect groups if they are not large enough?

I am new at statistics and I have problem that I have no idea how to solve. I have biological data, which includes expression levels (130 patients) for different alleles (I'm analysing SNP's) of ...
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28 views

Data Transformation with many 0 and 1

I'd like to transform my data (many 0 and 1) to reach normal Distribution. Is there a way to transform the following Distribution?
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2answers
47 views

What should be log-transforming advice?

I'm due to teach a workshop on statistics in a week or two, and one topic I will cover bothers me. The reason it bothers me, is that the advice I see, both in textbooks and here often on ...
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1answer
27 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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1answer
14 views

Data transformations and regression/k-means assumptions

I have a set of independent variables and one dependent variable. I am performing regression analysis and k-means with those variables and I am wondering the following: 1) After reading this ...
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16 views

Data transformed in order to satisfy regression assumptions but no effect

I am trying to use "Cursor" , "PostCursor" and "CTLE" to predict "left", and I added interactions and quandratic in the model. ...
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13 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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12 views

Wiener transformation - K-Apriori Algorithm

Wiener transformation is used to transform a binary data to a real data? How it works? Is there a R package that implements this transformation? I have been searching about Market Basket Analysis and ...
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1answer
38 views

Interpreting cubed root transformation

I’m running a linear regression where my response variable is mean satisfaction score of GP practices, while one of the predictor variables is funding received. I used a cube root transformation for ...
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1answer
24 views

How do I know if I adequately/correctly preprocessed my PCA/PCR data?

I'm an engineer with an interest in statistics, and my company sent me to a 1 week training in PCA/PCR (principal component analysis/regression) using The Unscrambler. I'm starting to apply these ...
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19 views

Data failed Levene's test for ANOVA. Trying to Log10 transform the data but I'm getting -Inf results!

I'm new to R and trying to run some two-way ANOVAs to test treatment effects in an ecology study. I've just tested my data using the Levene function: ...
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29 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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22 views

How to handle many-to-one data?

I'm trying a kaggle contest, just to improve my machine learning skills. The challenge I currently do involves many-to-one relational data. For instance, a person belongs to a municipality. A ...
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17 views

Common methods for transforming non-normal variable to close to normality

I have a list of time series which contain negative values. Right now I am transforming the time series to all positive values >0 and using the Box-Cox transformation to reduce non-normality. My ...
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1answer
110 views

Non-normally distributed data - Box-Cox transformation?

I have data that is not normally distributed. The problem seems to be that there are too many of one value relative to other values. What I have tried to make data normal: I have tried a log ...
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0answers
8 views

How to analyse skewed and unskewed data on SPSS?

Study design: I have shown participants a series of photos of themselves vs. other people's bodies (original and manipulated), and asked them to find the original. Their responses were recorded and ...
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1answer
96 views

How to create a data partition in R using categorical and numerical columns?

I'm using the createDataPartition method of the caret package as following: ...
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3 views

Non-spreadsheet-esque Data Import and Organization [migrated]

Basic Problem I have data of the form doc id 1 var1 A var2 B ... varStar 453 varStar 3432 varStar 32 ... varN doc var1 A var2 B (And so on) Where ...
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1answer
24 views

I have two sets of data, what is the best way to fit one set of data so it most closely matches the other

I have taken two sets of data with two different instruments. We know data set A taken with instrument A is very accurate and precise and that set B, while precise, is not accurate. Thus my data sets ...
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1answer
44 views

What is the advantage of transforming variables into First Difference of the Natural Log instead of % change from one period to the next?

I am dealing with macroeconomics time series data, and I build econometrics models. I am aware that some econometrists like to transform such variables as the First Difference in the Natural Log ...
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2answers
54 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
27 views

Email and IP String preprocessing for classification task

I am relatively new to the field of data-science, pardon my novice question. What are the available methods to convert email and ...
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36 views

How to analyze skewed and unskewed data on SPSS?

Study design: I have shown participants a series of photos of themselves vs. other people's bodies (original and manipulated), and asked them to find the original. Their responses were recorded and ...
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2answers
48 views

Log of Average v. Average of Log

I am constructing a dataset of monthly averages based on daily data. This dataset will be used for standard regression analysis. I anticipate wanting to transform the dependent variable, which has an ...
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1answer
50 views

Does ARIMA require normally distributed data? [duplicate]

I want forecast inflation using ARIMA model. My questions are: Does ARIMA require normally distributed input data? (Because my data—inflation—is not normal.) If ARIMA require normally ...
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15 views

Encode special values in continous predictors

I have continuous variable with missing values. Missing values are of different types (indicated by special values such as 991, 992). How do I best encode my data for logistic regression? I can create ...
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1answer
26 views

Data analysis: how to compare 2 variables from each subject across 3 groups of 200 subjects?

New here and not a statistician, am MD doing research. Need advice on best method for data analysis. I have 3 groups of 200 subjects each. We collected 2 data points (A,B) from each subject. Baseline ...
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6 views

Conducting a correlation when one of the covariates is a proportion

Is there anything that I should be wary of when conducting a correlation when one of the covariates is a proportion? I shall be running a Spearman rank analysis, correlating a continuous variable ...
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1answer
51 views

Linear regression with sine/cosine elements

How can you derive formula and regression coefficients for a regression model of a form $y(x)= A + B\, x + C\, \cos (2 \pi x) + D\, \sin (2 \pi x)$? I know that there are automatic tools who can do ...
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1answer
27 views

Whether to apply the logit transformation to proportional predictor variables in a multiple linear regression? [including proportions of 0.0%]

In a linear regression, I have a number of predictors variables that are expressed as proportions. The outcome variable is continuous. My residuals are not normally distributed, with a mild to ...
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1answer
48 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
62 views

Does one need to transform percentages/proportions for a multiple linear regression?

I am aware that one should transform percentages and proportions when using them in an ANOVA, due to the values being bounded by 0 and 1. I have seen suggestions that the best transformations are ...
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1answer
71 views

Interpreting test results on log-transformed data

I have data that is not normally distributed. I can log-transform it to be normally distributed, and then perform, for example, a t-test. But how do I interpret the results of the t-test? Do I have ...
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2answers
34 views

Which data transformation can improve the performance of MLP neural networks for classification?

I am trying to fit several MLP neural networks models with a single hidden layer using the caret R-package. My main concern now is in the preprocessing step. My train data features (16 in total) are ...
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0answers
18 views

Dealing with zeros when computing proportional change

I'm attempting to investigate the independence of the proportion of dividend payouts which is not linked to the movement of the stock index. The data I have is in the form of a list of dividend ...
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1answer
17 views

Transforming models in order to use linear least squares estimations

As a pre-exam question, I found a question asking to consider the following three models $$ y = \beta_{0}(x_{1})^{\beta_{1}}(x_{2})^{\beta_{2}}\epsilon $$ $$ y = \frac{1}{\beta_{0} + \beta_{1}x + ...
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28 views

Model design for queue position prediction

The goal of the model is to predict progression in position in a FIFO queue, given our current position and other predictor variables. This is progression in the sense that the number ahead of us in ...
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1answer
36 views

What is the origin of squaring centred data as way to model variances instead of means?

I recently came across this Answer by @mpiktas wherein he suggested a transformation of $y_i \rightarrow y_i^{\prime}$ $$y_i^{\prime} = (y_i - \overline{y})^2$$ followed by fitting a model for ...
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23 views

What is a good non cryptographic Hash for string feature translation?

What would be a good non cryptographic Hash function to use for converting string features to a numerical representation for feeding into machine learning algorithms? To explain the scenario my ...
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1answer
13 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: ...
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1answer
39 views

Converting a 5-point Likert scale to 0 to 30 range

Hi thanks for viewing my question. In my research I want to adopt a measure from prior work and apply it to a new context. The question related to a 5- point likert-scale, however, further reading ...
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0answers
7 views

Counts from aggregating on a time period for poisson modeling

I have a data set where each observation is a count==1. I also have common demographic data for each observation such as SEX, AGE, etc. I also have a time stamp variable, HOUR. I would like to fit the ...
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31 views

Logit or arcsine transformation for proportion in meta-analysis

I am performing a meta-analysis with 137 study arms. From each arm I have extracted a proportion of a disease. Here are my proportions: ...
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1answer
42 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 ...