# Tagged Questions

SAS is a proprietary cross-platform general-purpose statistical software package. [Official Website](http://www.sas.com/index.html)

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### Specifying the linear predictor, survival function and PDF of a log-normal survival distribution

Continuing on my exploration of the log-normal distribution, I'm working on reimplementing some code originally written for a Weibull/Exponential model for a log-normal model. Among the things it does ...
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### How are Kenward & Roger's degrees of freedom computed in PROC MIXED?

I run the following SAS model: ...
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### Are GAMMs/GLM the best choice for calculating number of germs on hands?

We would like your opinion on whether GAMMs are a good option and how best to go about implementing for the following: During a period of patient care, a nurse will accrue $Y$ colonies of bacteria on ...
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### How to specify in r spatial covariance structure similar to SAS sp(pow) in a marginal model?

I'm currently translating existing code from SAS to R. I'm working on longitudinal data (CD4 count over time). I have the following SAS code : ...
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### Prediction model problem

I am trying to design a model that can estimate the number of customers I will receive in every store every month using the number of customers I received every month in every store for the last five ...
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### prediction interval for heteroscedastic data

Here are some data: ...
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### Time Series: correcting the standard errors in a huge panel time series data set

I have stock returns at every 5 minute interval of each trading day for over 2 years for 40 stocks. I want to run a Fama-Macbeth regression by time interval (5min intervals) and then correct the ...
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### Convergence failure with step-by-step parameter estimates in SAS proc logistic using the OFFSET option

I'm trying to fit a logistic model of the following form: $$y \sim \frac{1}{1 + \exp(-\beta_X)}$$ where $$\beta_X = a_0 + a_1x_1 + a_2x_2 + a_3x_3 + a_4x_4 + a_5x_5$$ In my case, there is ...
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### SAS proc mixed empirical standard errors

I'm fitting a 3 level mixed model and trying to compute empirical rather than model-based standard errors for the fixed effects. When specifying the empirical option in PROC MIXED, I get a warning ...
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### Comparing two different but related datasets

Background: I used a principal component analysis to re-define neighborhood boundaries. Each neighborhood is made up of at least 2 census tracts. There were 40 neighborhoods in my old model. I have ...
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### How to get correct Covariance components in SAS Proc mixed? Struggling with infinite likelihoods and negative variance components

I am trying to estimate covariance components from PROC MIXED and having trouble with convergence problems in the REML approach when I use the NOBOUNDS option. Let me explain why I am using NOBOUNDS ...
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### Logistic Regression - Predicting an event with a couple time-related issues

I'm using logistic regression to predict the occurrence of tree carcasses falling after a mortality event. Data include a variety of topographic and tree characteristic variables and also time since ...
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### How do I interpret this McNemar's agreement plot generated by SAS?

I'm running a simple McNemar's test for agreement on the McNemar's example from Wikipedia. The test uses the following data: for patients of Hodgkin's disease. Running this SAS code: ...
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### What do I do if my predicted values are out of the dependent variable range?

I have built a beta regression model with log link for predicting adherence. My dependent variable's range is 0 to 1.When I used a test set to calculate the predicted values with the parameter ...
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### SAS PROC LOGISTIC: Hosmer and Lemeshow test is good but Gini is bad?

I am using PROC LOGISTIC along with Class statements to do binary logit model(default=1,non-default=0) on a bank loan dataset ...
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### How SAS calculates PROC GLM

I'm trying to do a pairwise test to calculate p-values between various products that are being evaluated by several assessors. I'm trying to reproduce what SAS is doing in R, and I'm running into an ...
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### How to calculate fitted values when using AdaBoost via gbm package in R? What does fitted values mean?

I poseted this question about two weeks ago. But it was closed because I cross-posted here and on SO. So I deleted the post on SO and re-post here. My question is as below. First of all I'm not ...
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### Multiplicative mixed models for analyzing variety-by-environment data

I got some nice data on multi-environmet trials (MET) data for genotype evaluation and would like to use some new developed techniques as discussed in Smith et. al 2005 Smith et. al 2005. I'm ...
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### Interactions in Log Transformed DV

I built a fixed effects model using time series cross sectional data. The model was built using PROC MIXED in SAS. There are 2 effect coded attributes in the model and inteactions. One dummy ...
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### Repeated Measures in R, SAS or SPSS: Whale Body Temperature Data

I have a question regarding a repeated measures experiment. I have 5 whales (randomly selected) that I recorded body temperature on. Data was collected via satellite, programmed to transmit records at ...
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### Difference between GLM with intercept of subject VS repeated-measures ANOVA? [SAS code]

I've spent days trying to determine the difference between these two methods, which, as best I can tell, represent the univariate and multivariate approaches to a within-subjects design. Can anybody ...
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### Survival analysis in SAS-is there a way to include a random effect with interval censored data?

I'm trying to use some form of survival analysis (e.g. accelerated failure time or proportional hazards) to study seed germination time. My data is interval censored (also called "grouped-time") and ...
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### Avoiding the Generalized Variance Formula for the NYC Housing and Vacancy Survey

I am attempting to devise a replication-based survey design that closely replicates a taylor-series design used by the US Government publication - where I do not have access to all of the ...
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### SAS error: variance covariance matrix singular

I am now working with a classmate on an estimate of an Almost Ideal Demand System for tobacco consumption. We have chosen to make an AIDS regression using goods tobacco and alchol, and the CPI price ...
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### Covariate in generalized linear model with binary DV

I am comparing an offender group with a control group on a certain task in a generalized linear model with accuracy (0-1) as the DV. The reviewers criticized me by mentioning that one group was ...
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### Sum of Squares reduction test: Convergence criteria met, but not all parameters of the model estimated

Background: I am using weighted non-linear regression to model the growth of plant organs, with dummy variables for different species. I am using a sum of squares reduction test (SSRT) to compare the ...
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### Predicting a time-series based on level, season, and cycle

I have time-series data for stock price. A sample of dataset is given below: ...
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### Simulating C4.5 algorithm using Decision Tree node in SAS Enterprise Miner 6.2.

In SAS Enterprise Miner 6.2 it's possible to approximate CHAID and CART methods using Decision Tree node, according to SAS Help, but there is nothing about C4.5 algorithm. How can I mimic C4.5 ...
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### Building a mixed model for multi-location split plot over 2 years in SAS

For the last 3 weeks I have been reading books, papers and internet sources incl. cross validated but could not find something that would work in my case. I have data from a split-plot field trial. ...
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### Spline df selection in a General Additive Poisson Model problem

I've been fitting some time series data using a Poisson general additive model using SAS's PROC GAM. Generally speaking, I've been having it's built-in generalized ...
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### SAS optimal binning

In SAS enterprise miner we have the optimal binning feature which allows you to transform continuous variables into an ordered set of bins. The binning, as I read from one of their docs, is done so ...
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### SAS fails to fit a mixed model

Here are some simulated data: ...
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### How to draw B-spline plots via the PROC GLIMMIX procedure in SAS?

Recently I found that the PROC GLIMMIX procedure in SAS added a statement effect, which can handle B-spline in models. I tried ...
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### Interpretation of a log likelihood function for PROC NLMIXED in SAS

I have a data set of skewed nutrient intake values, from around 7800 individuals, of whom around 3000 had two measures of daily nutrient intake (the others only had one measure), so this is a repeated ...
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### Nonlinear mixed methods, Monte Carlo simulation and appropriate use of weighting for population distribution estimation

Note: I do not have access to SAS so I am trying to interpret the code off the macro syntax. I have frequency-weighted data of nutrition intakes. The frequency ...
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### How is the SAS REPLICATE statement in PROC NLMIXED different from a FREQ statement?

Note: I do not have access to SAS to work this out for myself. I'm trying to work out the difference between the FREQ statement ...
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### Good resources about reversible-jump MCMC sampler in R

Please help me to find out simple (I mean useful with little knowledge on Bayesian statistics) resources: To learn MCMC and perform general linear or mixed models To learn different sampling ...
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### Different results from SAS PROC MIXED procedure and R lme function

I have 3(treatment)x3(period)x6(sequence) crossover design data. I have used SAS PROC MIXED procedure and I got the results with following code: ...
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### Proc GENMOD estimate statement with 2 continuous variables?

I'm testing an ordinal scale measuring dyskinesia (range=0-4) via proc genmod, with the independent variables in the model being Drug1 and Drug2. Both of these variables are continuous. I want to ...
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### Reporting predicted outcome of mixed effects models

I am analyzing some group-randomized longitudinal trial data with three time points using mixed effects model. Some people missed 1-2 time points, and I didn't exclude any cases with missing dependent ...
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### How big of a dataset can R or SAS handle for regression?

On a standard computer (~3-6gb RAM) with 2 - 4 processors. What are the size restrictions on a matrix of data for R or SAS?
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### Estimating Smoothing Parameters Simultaneously with Regression Coeffecients

I am developing a forecasting model that relies on a smoothed leading indicator. The indicator is the ratio of two smoothed series, and the forecasting regression equation uses a lagged value of the ...
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### Degrees of freedom for mixed model

Using data and code the example from http://www.ats.ucla.edu/stat/sas/faq/anovmix1.htm: ...
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### What is the Survival Function using SAS LIFEREG with lognormal distribution?

I am trying to plot the survival curve using output from PROC LIFEREG with a lognormal distribution. Is my formula for the survival function (prob[i], where i is time) correct? Below is my SAS code. ...
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### Media or market mix modeling?

Can anyone tell me how to build media mix model? Is it similar to market mix model? What are the steps and variables in the model? If I want to build in SAS which procedure should I use?
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### Experimental design & model

I'm testing the effect of land history and soil organisms on the growth of Stinging nettle. To investigate the effect of land history ("hist") on growth, soil samples ("sample") were collected at 10 ...
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### Frequency Table for Repeated Measures

I've 12 unique subjects, and in total I've almost 1700 observations. I've an ordinal response variable (has 4 levels) and 3 categorical covariates (each one has different levels 3, 5, 2, and 4 ...
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### Results from multinomial ordinal logistic regression model

I've an ordinal response variable (has 4 levels) and 3 categorical covariates (each one has different levels 3, 5, 2, and 4 respectively). We also are dealing with repeated observations. I fitted a ...