Tagged Questions

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

63 views

Can I assume that the expected value of this log ratio is 0?

I am taking two measurements from subjects: measurement A and measurement B. I have some strong theoretical reasons to think that my measurements of A and B should on average be the same as each ...
14 views

Interpret log ratio coefficient when outcome is also log ratio coefficient [duplicate]

If I have a log-log regression, where the outcome is change from baseline or: (Δln(Price))=b 0 +b 1 ×(Δln(emp)) Where Δ(ln(emp))=ln(employment growth_year2)−ln(employment growth_year1) and Δ(ln(...
39 views

Does “Log loss” refer to Logarithmic loss or Logistic loss?

I know I've seen it both ways, so is there a difference between the two, and which one is more commonly referred to?
35 views

Interpreting a Cox regression model when one predictor is log-transformed

In my model I am considering the rate of hospital re-admission (outcome) and my covariates are non-log transformed while my main variable of interest - direct cost of home rehabilitation - is ln ...
20 views

Log transform in time series

After taking the $\log(1+x)$ transformation on a time series, I am guessing which features should I use as predictors: $\text{mean}(\log(1+x))$ vs $\log(1+\text{mean}(x))$ $\text{std}(\log(1+x))$ vs ...
84 views

How can I calculate variance of a very large random variable?

I'm implementing an algorithm which recieves as input samples from a random variable with an unknown distribution. The random variable is extremely large so my input is logarithmic, and still large (...
27 views

19 views

How to measure if data conforms to logarithmic curve

I am collecting data that should closely resembles a logarithmic curve. I have many datasets. How can I measure how closely each dataset resembles a logarithmic curve and call out any outlying ...
56 views

log-log regression in r

I want to do a log-log regression in R. I managed to do a simple linear and log-linear regression by using this code: ...
209 views

If my goal is to test the absolute change of the ratios, can I compare the ratios directly without log transformation?

Ratios (e.g. $Z$=$Y$/$X$) are frequently used (e.g. fold-changes in mRNA or protein expression, body mass index [BMI], etc.). Many people advise that variables coded as ratios (e.g. fold-change) ...
22 views

setting log-uniform priors in Stan

I have been using Stan for a couple months now and I want to adopt a log-uniform prior on some parameter array real theta[N]. I want to do something like a ...
18 views

Interpretation of LOGIT transformed predictor when outcome variable is LOG transform

I have a linear mixed effect model in which the dependent variable is a log-transformed frequency of livestock predation predation, and there are three predictor ...
48 views

122 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-...
1k views

In statistics, should I assume $\log$ to mean $\log_{10}$ or the natural logarithm $\ln$?

I'm studying statistics and often come across formulae containing the log and I'm always confused if I should interpret that as the standard meaning of ...
13 views

Amplitude and confidence intervals using log transformed dependent variable

I have two questions: - I am fitting a cosinor model to estimate the seasonality of vitamin D levels, which is natural-log transformed. Now, I will estimate the amplitude = sqrt((beta1^2)+(beta2^2)), ...
11 views

Logarithmic transformation and regression for Product sequence

So, I have an equation like below: $k_{A}*A*k_{B}*B*k_{C}*C=f$ (eq1) The only value I have is A,B, C, and f. I want to estimate $k_{x}$ and I have several equation so that I think it is possible ...
40 views

Modeling a Y~Log(X+constant) equation

I have this data set of Xs and Ys. I am trying to fit an equation to it using R, of the form: y ~ log(x+constant) Any ideas how to do it?
68 views

Conflicting interpretations for coefficient of log transformed predictor

If you think this is a duplicate, please have a look at the last paragraph. In a regression model where both dependent ($Y$) and independent ($X$) variable are in natural logs, what is the exact ...
24 views

Inverting logarithmic output from VAR model

I'm working on a VAR model and am doing a log transformation of the raw data. x = log(x) After differencing, running various tests and running a VAR(2) model, I ...
48 views

Why do the predictions of a linear (log-log) model not approximate those of a nonlinear (power) model?

I am having trouble using a linear (log-log) model to approximate the predictions of a nonlinear (power) model. I wish to plot the predictions of the linear model on untransformed axes, and I believe ...
78 views

14 views

Trendline for data with two phases

I'd like to know how to fit a curve to a set of data that has two phases. For the below data I've tried using a third order polynomial, but I think that's overfitting the data and I've tried using ...
73 views

Log transform produce sign change on coefficients

I want to regress $x_1, x_2, x_3$ and $x_4$ on $y$. Question: When fitting a regression model in the regular fashion without any transformations the coefficient for $x_4$ is positive. However when I ...
36 views

How should I deal with a nonlinear objective function in linear programming? [closed]

What I tried: Let $x_i$ be the number of units in compartment $i$. We want to minimise the probability $$z = 0.3^{x_1} 0.4 ^{x_2} 0.2^{x_3}$$ s.t. Space: $$30x_1 + 40x_2 + 20x_3 \le 400$$ ...
19 views

How to get real value from log adjustement value

I am looking for some data for my research, and found reliable graph which showed the correlation of fetal weight and gestational age which is what I want. However, the weight in that scatter plot ...
68 views

107 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. ...
79 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 ...
31 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 ...
38 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 data;...
28 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 ...
63 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 ...
32 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 ...