Questions tagged [logarithm]
The logarithm of a number is the power to which the base must be raised to get the number.
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Interquartile range when back-transformed mean on log-scale is not equal to median on normal scale
I have 2x10 observations that follow a non-normal distribution. They are perfectly distributed on log-scale.
From what I've learned, the back-transformation of the mean on log-scale should be a "...
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In R Limma's `normalizeMedianValues` function, why is its operations preceded with a log transformation followed by an exponential transformation?
In the function normalizeMedianValues in the package limma, column counts are normalised such that their column medians are ...
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How can I compare median survival times statistically based on Kaplan Meier curves/Log-rank test
I have a few question concerning the log-rank test and would be glad if anyone can answer these:
First of all I am wondering which benefits one has when plotting KM curves of two groups if one already ...
user390565
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Back transforming log data
I have a dataset with biomass, dbh, height, wood density, site, and species. As data were not normally distributed, I converted biomass, dbh and wd using the log() ...
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Carrying out statistics on -log(p)
I have an $n \times m$ matrix, where each row $\mathbf{v}_i$, for $i \in \{1, \ldots , n\}$, consists of some permutation of the set $\{1, \ldots, m\}$ (and so in particular, each $\mathbf{v}_{i, j} \...
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How to deal with negative values after subtracting the background?
I am working with Luminex data and have a question regarding the treatment of negative values after subtracting the background average. Specifically, I would like to know if these negative values need ...
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How do you interpret the PCA Score from data that has previously been logarithmic transformed?
I want to make financial inclusion by using PCA. Before I did PCA, I had done a logarithmic transformation on the data because my data was positive and highly skewed (I saw this from Jolliffe's book ...
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ANOVA: contrast to ratio of adjusted geometric means
Could you, please, help me with the following problem?
Suppose we have a one-way ANOVA with a single 2-level factor. The dependent variable is a logarithmized value: $y_i = log(Y_i)$.
$y_{iz} = \mu + ...
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Interpretation of coefficient on an interaction term of log(continuos x)*log(continuous y)
I would like to ask a question regarding the interpretation of log-log interaction term in the Two-way fixed effect model. I have the following regression model:
y_it = 𝛽_0 + 𝛽2[ln(price_it)*ln(...
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ARIMAX model for Google trends: trouble with lots of zeros
I want to apply ARIMAX model on Google trends. I used python package to get daily data. However, this data contains a lot of zeros, so if I do first difference of logs, I see a lot of (inf) in python.
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Can I transform variables to comply with conditions on order of integration in an ARDL model?
If log variable have a unit root, can you then difference it?
For ARDL model variables should not be I(2) or more. Variables of log form are I(2). Would it be a problem to difference it.
What I am ...
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First difference of logs of negative numbers causes trouble
I have the following problem: I have a timeseries with the prices for a few futures, which is non-stationary (according to ADF test). If I apply first difference of logs, ADF shows stationarity.
But I ...
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Can glm(m) model estimates be negative after back transforming?
I have made three generalized linear models, one with zero-inflated Poisson, the second with negative binomial, and the third with binomial conditional distributions. I am now trying to interpret the ...
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Statistical comparison of two (log) probabilities
Using R, I built 2 logistic regression models (with outcome variable being depression status - present or absent) and used leave one out cross validation to obtain predicted values for the dataset. I ...
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Numerically stable transformation of log-likelihoods to probability [closed]
I have the following problem: I have log-likelihoods that need to be transformed to probabilities. One thing I have attempted is the following. Define $\kappa_{s} := \log \int p (\theta | X_s) \text{d}...
