I am training multiple 'treebag' models in R. I loop through a data set, where each iteration I define a specific subset based on a feature in the set and train on that subset. I could save each result to disk, but I was hoping to save all the models to a single data frame or data table. I am not sure if this is at all possible. The data frame/table could have numerous classes (numeric and character), however I would like to add a completed model.
To start, is it even possible to assign multiple models to a single column, where each model is assigned to a different row in a data frame or data table?
Any ideas on how this could work is greatly appreciated.
Related
I want to use the activity_stats function (and others) on a data set that has several dozen subjects. Based on the documentation, it looks like I have to make a separate data frame for each subject, and then run the functions on each individual data frame. Is that the case?
https://github.com/martakarass/arctools#using-arctools-package-to-compute-physical-activity-summaries
Example output of tab_model
I have created a table from tab_model that includes multiple models and wish to extract all 'p-values' and 'Estimates/Odds Ratio' to create a data frame that includes these. Output of tab_model is an html file. I am unable to find a function to pull this info in accordance, any ideas on how I could do this?
For example, I want to retrieve all p-values and Estimates for variable 'age' in all of my models...Only 3 in example image but I have hundreds
You should get these values from the regression models themselves, instead of outputting them to a HTML-table, and then extract them.
Without further knowledge of your process and data it is difficult to provide a more concrete answer.
I conduct a large number of regression analyses using ols and cph (different models, sensitivity analyses etc) which takes on my computer around two hours. Therefore, I would like to save these models so that I don't have to re-run the same analyses every time I want to work with them. The models all have very structured names, so I can create a list of names as follows:
model.names <- list()[grep("^im", ls())
But how can I use this to save those models? Could they be placed into a data frame?
I think you are looking for save()
save writes an external representation of R objects to the specified file. The objects can be read back from the file at a later date by using the function load or attach (or data in some cases).
I start with a data.frame (or a data_frame) containing my dependent Y variable for analysis, my independent X variables, and some "Z" variables -- extra columns that I don't need for my modeling exercise.
What I would like to do is:
Create an analysis data set without the Z variables;
Break this data set into random training and test sets;
Find my best model;
Predict on both the training and test sets using this model;
Recombine the training and test sets by rows; and finally
Recombine these data with the Z variables, by column.
It's the last step, of course, that presents the problem -- how do I make sure that the rows in the recombined training and test sets match the rows in the original data set? We might try to use the row.names variable from the original set, but I agree with Hadley that this is an error-prone kludge (my words, not his) -- why have a special column that's treated differently from all other data columns?
One alternative is to create an ID column that uniquely identifies each row, and then keep this column around when dividing into the train and test sets (but excluding it from all modeling formulas, of course). This seems clumsy as well, and would make all my formulas harder to read.
This must be a solved problem -- could people tell me how they deal with this? Especially using the plyr/dplyr/tidyr package framework?
I am working on developing and optimizing a linear model using the lm() function and subsequently the step() function for optimization. I have added a variable to my dataframe by using a random generator of 0s and 1s (50% chance each). I use this variable to subset the dataframe into a training set and a validation set If a record is not assigned to the training set it is assigned to the validation set. By using these subsets I am able to estimate how good the fit of the model is (by using the predict function for the records in the validation set and comparing them to the original values). I am interested in the coefficients of the optimized model and in the results of the KS-test between the distributions of the predicted and actual results.
All of my code was working fine, but when I wanted to test whether my model is sensitive to the subset that I chose I ran into some problems. To do this I wanted to create a for (i in 1:10) loop, each time using a different random subset. This turned out to be quite a challenge for me (I have never used a for loop in R before).
Here's the problem (well actually there are many problems, but here is one of them):
I would like to have separate dataframes for each run in the loop with a unique name (for example: Run1, Run2, Run3). I have been able to create a variable with different strings using paste(("Run",1:10,sep=""), but that just gives you a list of strings. How do I use these strings as names for my (subsetted) dataframes?
Another problem that I expect to encounter:
Subsequently I want to use the fitted coefficients for each run and export these to Excel. By using coef(function) I have been able to retrieve the coefficients, however the number of coefficients included in the model may change per simulation run because of the optimization algorithm. This will almost certainly give me some trouble with pasting them into the same dataframe, any thoughts on that?
Thanks for helping me out.
For your first question:
You can create the strings as before, using
df.names <- paste(("Run",1:10,sep="")
Then, create your for loop and do the following to give the data frames the names you want:
for (i in 1:10){
d.frame <- # create your data frame here
assign(df.name[i], d.frame)
}
Now you will end up with ten data frames with ten different names.
For your second question about the coefficients:
As far as I can tell, these don't naturally fit into your data frame structure. You should consider using lists, as they allow different classes - in other words, for each run, create a list containing a data frame and a numeric vector with your coefficients.
Don't create objects with numbers in their names, and then try and access them in a loop later, using get and paste and assign. The right way to do this is to store your elements in an R list object.