I want to estimate a multilevel ordered logistic model and afterwards access the model matrix. When running a simplified example from ?clmm:
library("ordinal")
mod1 <- clmm(SURENESS ~ PROD + (1|RESP), data = soup)
model.matrix(mod1)
I get the error message Error in eval(predvars, data, env) : object 'SURENESS' not found. From other packages I expected that setting parameters like model = TRUE the data going in are also exported to the estimated model, but here all relevant parameters seem to be set accordingly by default. Did I miss some parameters or elements from mod1 (I went through attributes(mod1) but did not find a model matrix.
Strangely if I set a random data.frame, it works:
set.seed(123)
df <- data.frame(y = factor(sample(c("A", "B", "C"), size = 1000, replace = TRUE), ordered = TRUE),
x = rnorm(1000),
id = factor(rep(1:10, each = 100)))
mod2 <- clmm(y ~ 1 + x + (1|id), data = df)
model.matrix(mod2)
So what's the difference between mod1 and mod2 and how do I get a model.matrix from mod1?
I do not think model.matrix(mod2) works for clmm objects. However, you can try to build a parallel model for the fixed effects part using functions like 'polr' and apply model.matrix() to the output object. The random-effects part can be fixed separately by using the clmm output.
Related
I am attempting to get clustered SEs (at the school level in my data) with data that is both imputed (MICE) and weighted (CBPS). I have tried a couple different approaches that have thrown different errors.
This is what I have to start, which works fine:
library(tidyverse)
library(mice)
library(MatchThem)
library(CBPS)
tempdata <- mice(d, m = 10, maxit = 50, meth = "pmm", seed = 99)
weighted_data <- weightthem(trtmnt ~ x1 + x2 + x3,
data = tempdata,
method = "cbps",
estimand = "ATT")
Using this (https://www.r-bloggers.com/2021/05/clustered-standard-errors-with-r/) as a guide, I attempted all 3, which all resulted in various types of error messages.
My data is in a restricted server so unfortunately I can't bring it into here to reproduce things exactly, although if it's useful I could attempt to recreate some sample data.
So attempting with estimatr first, I get this error:
m1 <- estimatr::lm_robust(outcome ~ trtmnt + x1 + x2 + x3,
clusters = schoolID,
data = weighted_data)
Error in eval_tidy(mfargs[[da]], data = data) :
object 'schoolID' not found
I have no clue where the schoolID variable would have dropped out/not be recognized. It isn't part of the weighting procedure but it should still be in the data frame...if I use it as a covariate in a standard model without clustering, it's there.
I also attempted with miceadds and got this error:
m2 <- miceadds::lm.cluster(outcome ~ trtmnt + x1 + x2 + x3,
cluster = "schoolID",
data = weighted_data)
Error in as.data.frame.default(data) :
cannot coerce class `"wimids"` to a data.frame
And finally, with sandwich and lmtest:
library(sandwich)
library(lmtest)
m3 <- weighted_models <- with(weighted_data,
exp=lm(outcome ~ trtmnt + x1 + x2 + x3))
msandwich <- coeftest(m3, vcov = vcovCL, cluster = ~schoolID)
Error in UseMethod("estfun") :
no applicable method for `estfun` applied to an object of class "c(`mimira`, `mira`)"
Any ideas on any of the above methods, or where to go next?
You were really close. You need to use with(weighted_data, .) to fit a model in your weighted datasets, and you need to use estimatr::lm_robust() to get the clustered standard errors. So try the following:
weighted_models <- with(weighted_data,
estimatr::lm_robust(outcome ~ trtmnt + x1 + x2 + x3,
cluster = schoolID))
Your first and second approaches were incorrect because you supplied weighted_data to a single model as if it were a data frame, but it's not; it's a complicated wimids object. You need to use the with() infrastructure to fit a model to the imputed weighted data.
Your third approach was close, but coeftest() needs to be used on a single model, not a mimira object, which contains all the models fit the imputed datasets. Although you can use coeftest() inside with() with mira objects, you cannot do so with mimira objects from MatchThem. This is where estimatr::lm_robust() comes in since it is able to apply the clustering within each imputed dataset.
I also recommend you take a look at this blog post on estimating treatment effects after weighting with multiply imputed data. The only difference in your case to the code presented in the post is that you would change vcov = "HC3" to vcov = ~schoolID in whichever function you use.
I am fitting a model using a random site-level effect using a generalized additive model, implemented in the mgcv package for R. I had been doing this using the function gam() however, to speed things up I need to shift to the bam() framework, which is basically the same as gam(), but faster. I further sped up fitting by passing the options bam(nthreads = N, discrete=T), where nthreads is the number of cores on my machine. However, when I use the discretization option, and then try to make predictions with my model on new data, while ignoring the random effect, I consistent get an error.
Here is code to generate example data and reproduce the error.
library(mgcv)
#generate data.
N <- 10000
x <- runif(N,0,1)
y <- (0.5*x / (x + 0.2)) + rnorm(N)*0.1 #non-linear relationship between x and y.
#uninformative random effect.
random.x <- as.factor(do.call(paste0, replicate(2, sample(LETTERS, N, TRUE), FALSE)))
#fit models.
fit1 <- gam(y ~ s(x) + s(random.x, bs = 're')) #this one takes ~1 minute to fit, rest faster.
fit2 <- bam(y ~ s(x) + s(random.x, bs = 're'))
fit3 <- bam(y ~ s(x) + s(random.x, bs = 're'), discrete = T, nthreads = 2)
#make predictions on new data.
newdat <- data.frame(runif(200, 0, 1))
colnames(newdat) <- 'x'
test1 <- predict(fit1, newdata=newdat, exclude = c("s(random.x)"), newdata.guaranteed = T)
test2 <- predict(fit2, newdata=newdat, exclude = c("s(random.x)"), newdata.guaranteed = T)
test3 <- predict(fit3, newdata=newdat, exclude = c("s(random.x)"), newdata.guaranteed = T)
Making predictions with the third model which uses discretization throws this error (which the other two do not):
Error in model.frame.default(object$dinfo$gp$fake.formula[-2], newdata) :
variable lengths differ (found for 'random.x')
In addition: Warning message:
'newdata' had 200 rows but variables found have 10000 rows
How can I go about making predictions for a new dataset using the model fit with discretization?
newdata.gauranteed doesn't seem to be working for bam() models with discrete = TRUE. You could email the author and maintainer of mgcv and send him the reproducible example so he can take a look. See ?bug.reports.mgcv.
You probably want
names(newdat) <- "x"
as data frames have names.
But the workaround is just to pass in something for random.x
newdat <- data.frame(x = runif(200, 0, 1), random.x = random.x[[1]])
and then do your call to generate test3 and it will work.
The warning message and error are the result of you not specifying random.x in the newdata and then mgcv looking for random.x and finding it in the global environment. You should really gather that variables into a data frame and use the data argument when you are fitting your models, and try not to leave similarly named objects lying around in your global environment.
I am trying to implement lasso regression for my sales prediction problem. I am using glmnet package and cv.glmnet function to train the model.
library(glmnet)
set.seed(123)
model = cv.glmnet(as.matrix(x = train[, -which(names(train) %in% "Sales")]),
y = train$Sales,
alpha = 1,
lambda = 10^seq(4,-1,-0.1))
best_lambda = model$lambda.min
lasso_predictions_valid <- predict(model,s = best_lambda,type = "coefficients")
After I read few articles about implementing lasso regression I still don't know how to add my test data on which I want to apply the prediction. There is newx argument to be added to predict function that I do not know also. I mean in most regression types we have newdata or data argument that we fill our test data to it.
I think there is an error in your lasso_predictions_valid, you shouldn't put valid$sales as your newx, as I believe this is the actual sales number.
Once you have created the model with the train set, then for newx you need to pass matrix values of x that you want to make predictions on, I guess in this case it will be your validation set.
Looking at your example code above, I think your predict line should be something like:
lasso_predictions_valid <- predict(model, s = best_lambda,
newx = as.matrix(valid[, -which(names(valid) %in% "Sales")]),
type = "coefficients")
Then you should run your RMSE() line:
RMSE(lasso_predictions_valid, valid$Sales)
The working data looks like:
set.seed(1234)
df <- data.frame(y = rnorm(1:30),
fac1 = as.factor(sample(c("A","B","C","D","E"),30, replace = T)),
fac2 = as.factor(sample(c("NY","NC","CA"),30,replace = T)),
x = rnorm(1:30))
The lme model is fitted as:
library(lme4)
mixed <- lmer(y ~ x + (1|fac1) + (1|fac2), data = df)
I used bootMer to run the parametric bootstrapping and I can successfully obtain the coefficients (intercept) and SEs for fixed&random effects:
mixed_boot_sum <- function(data){s <- sigma(data)
c(beta = getME(data, "fixef"), theta = getME(data, "theta"), sigma = s)}
mixed_boot <- bootMer(mixed, FUN = mixed_boot_sum, nsim = 100, type = "parametric", use.u = FALSE)
My first question is how to obtain the coefficients(slope) of each individual levels of the two random effects from the bootstrapping results mixed_boot ?
I have no problem extracting the coefficients(slope) from mixed model by using augment function from broom package, see below:
library(broom)
mixed.coef <- augment(mixed, df)
However, it seems like broom can't deal with boot class object. I can't use above functions directly on mixed_boot.
I also tried to modify the mixed_boot_sum by adding mmList( I thought this would be what I am looking for), but R complains as：
Error in bootMer(mixed, FUN = mixed_boot_sum, nsim = 100, type = "parametric", :
bootMer currently only handles functions that return numeric vectors
Furthermore, is it possible to obtain CI of both fixed&random effects by specifying FUN as well?
Now, I am very confused about the correct specifications for the FUN in order to achieve my needs. Any help regarding to my question would be greatly appreciated!
My first question is how to obtain the coefficients(slope) of each individual levels of the two random effects from the bootstrapping results mixed_boot ?
I'm not sure what you mean by "coefficients(slope) of each individual level". broom::augment(mixed, df) gives the predictions (residuals, etc.) for every observation. If you want the predicted coefficients at each level I would try
mixed_boot_coefs <- function(fit){
unlist(coef(fit))
}
which for the original model gives
mixed_boot_coefs(mixed)
## fac1.(Intercept)1 fac1.(Intercept)2 fac1.(Intercept)3 fac1.(Intercept)4
## -0.4973925 -0.1210432 -0.3260958 0.2645979
## fac1.(Intercept)5 fac1.x1 fac1.x2 fac1.x3
## -0.6288728 0.2187408 0.2187408 0.2187408
## fac1.x4 fac1.x5 fac2.(Intercept)1 fac2.(Intercept)2
## 0.2187408 0.2187408 -0.2617613 -0.2617613
## ...
If you want the resulting object to be more clearly named you can use:
flatten <- function(cc) setNames(unlist(cc),
outer(rownames(cc),colnames(cc),
function(x,y) paste0(y,x)))
mixed_boot_coefs <- function(fit){
unlist(lapply(coef(fit),flatten))
}
When run through bootMer/confint/boot::boot.ci these functions will give confidence intervals for each of these values (note that all of the slopes facW.xZ are identical across groups because the model assumes random variation in the intercept only). In other words, whatever information you know how to extract from a fitted model (conditional modes/BLUPs [ranef], predicted intercepts and slopes for each level of the grouping variable [coef], parameter estimates [fixef, getME], random-effects variances [VarCorr], predictions under specific conditions [predict] ...) can be used in bootMer's FUN argument, as long as you can flatten its structure into a simple numeric vector.
I'm using the MuMln package in R to get an averaged model (http://www.inside-r.org/packages/cran/MuMIn/docs/model.avg), and predict from that. The package also includes a predict function specifically for an object returned by model.avg (http://www.inside-r.org/node/123636). I've tried using the examples listed, code as follows:
# Example from Burnham and Anderson (2002), page 100:
fm1 <- lm(y ~ X1 + X2 + X3 + X4, data = Cement)
ms1 <- dredge(fm1)
# obtain model average for AIC delta <2
avgm <- model.avg(ms1, subset=delta<2)
# predict from the averaged model
averaged.full <- predict(avgm, full = TRUE)
But I keep getting
Error in predict.averaging(avgm, full = TRUE): can predict only from 'averaging' object containing model list
which I don't understand, because I did follow the examples and used an object returned by model.avg. Am I missing something?
When you create an "averaging" object directly from "model.selection" object, it does not contain the component models, which are required for predict to work. You can use model.avg(..., fit = TRUE) which will fit the models again.
To avoid fitting the models twice, you can first create a list of all models with
lapply(dredge(..., evaluate = FALSE), eval) and afterwards
use model.avg(..., subset = ...) on it.