Posted on Categories Coding, Opinion, Programming, Statistics, TutorialsTags , , , Leave a comment on R Tip: Use Slices

R Tip: Use Slices

R tip: use slices.

SliceOMatic

R has a very powerful array slicing ability that allows for some very slick data processing.

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Posted on Categories Opinion, Programming, StatisticsTags , , , 12 Comments on Neglected R Super Functions

Neglected R Super Functions

R has a lot of under-appreciated super powerful functions. I list a few of our favorites below.


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Atlas, carrying the sky. Royal Palace (Paleis op de Dam), Amsterdam.

Photo: Dominik Bartsch, CC some rights reserved.

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Posted on Categories Coding, Opinion, Pragmatic Data Science, Statistics, TutorialsTags , , , , , , , Leave a comment on R Tip: Think in Terms of Values

R Tip: Think in Terms of Values

R tip: first organize your tasks in terms of data, values, and desired transformation of values, not initially in terms of concrete functions or code.

I know I write a lot about coding in R. But it is in the service of supporting statistics, analysis, predictive analytics, and data science.

R without data is like going to the theater to watch the curtain go up and down.

(Adapted from Ben Katchor’s Julius Knipl, Real Estate Photographer: Stories, Little, Brown, and Company, 1996, page 72, “Excursionist Drama 2”.)

Usually you come to R to work with data. If you think and plan in terms of data and values (including introducing more data to control processing) you will usually work in much faster, explainable, and maintainable fashion.

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Posted on Categories Coding, TutorialsTags , , , 4 Comments on R Tip: Use Named Vectors to Re-Map Values

R Tip: Use Named Vectors to Re-Map Values

Here is an R tip. Want to re-map a column of values? Use a named vector as the mapping.

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Posted on Categories Coding, Opinion, Statistics, TutorialsTags , , , , , , , 1 Comment on R Tip: Use let() to Re-Map Names

R Tip: Use let() to Re-Map Names

Another R tip. Need to replace a name in some R code or make R code re-usable? Use wrapr::let().



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Posted on Categories Coding, TutorialsTags , , , 4 Comments on R Tip: Use stringsAsFactors = FALSE

R Tip: Use stringsAsFactors = FALSE

R tip: use stringsAsFactors = FALSE.

R often uses a concept of factors to re-encode strings. This can be too early and too aggressive. Sometimes a string is just a string.


800px Sigmund Freud by Max Halberstadt cropped

It is often claimed Sigmund Freud said “Sometimes a cigar is just a cigar.”

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Posted on Categories data science, Practical Data Science, Pragmatic Data Science, Pragmatic Machine Learning, Statistics, TutorialsTags , , , , , , 9 Comments on R Tip: Use the vtreat Package For Data Preparation

R Tip: Use the vtreat Package For Data Preparation

If you are working with predictive modeling or machine learning in R this is the R tip that is going to save you the most time and deliver the biggest improvement in your results.

R Tip: Use the vtreat package for data preparation in predictive analytics and machine learning projects.

Vtreat

When attempting predictive modeling with real-world data you quickly run into difficulties beyond what is typically emphasized in machine learning coursework:

  • Missing, invalid, or out of range values.
  • Categorical variables with large sets of possible levels.
  • Novel categorical levels discovered during test, cross-validation, or model application/deployment.
  • Large numbers of columns to consider as potential modeling variables (both statistically hazardous and time consuming).
  • Nested model bias poisoning results in non-trivial data processing pipelines.

Any one of these issues can add to project time and decrease the predictive power and reliability of a machine learning project. Many real world projects encounter all of these issues, which are often ignored leading to degraded performance in production.

vtreat systematically and correctly deals with all of the above issues in a documented, automated, parallel, and statistically sound manner.

vtreat can fix or mitigate these domain independent issues much more reliably and much faster than by-hand ad-hoc methods.
This leaves the data scientist or analyst more time to research and apply critical domain dependent (or knowledge based) steps and checks.

If you are attempting high-value predictive modeling in R, you should try out vtreat and consider adding it to your workflow.

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Posted on Categories Coding, Statistics, TutorialsTags , , , 1 Comment on R Tip: Introduce Indices to Avoid for() Class Loss Issues

R Tip: Introduce Indices to Avoid for() Class Loss Issues

Here is an R tip. Use loop indices to avoid for()-loops damaging classes.

Below is an R annoyance that occurs again and again: vectors lose class attributes when you iterate over them in a for()-loop.

d <- c(Sys.time(), Sys.time())
print(d)
#> [1] "2018-02-18 10:16:16 PST" "2018-02-18 10:16:16 PST"

for(di in d) {
  print(di)
}
#> [1] 1518977777
#> [1] 1518977777

Notice we printed numbers, not dates/times. To avoid this problem introduce an index, and loop over that, not over the vector contents.

for(ii in seq_along(d)) {
  di <- d[[ii]]
  print(di)
}
#> [1] "2018-02-18 10:16:16 PST"
#> [1] "2018-02-18 10:16:16 PST"

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Posted on Categories Coding, TutorialsTags , , Leave a comment on R Tip: Use vector(mode = "list") to Pre-Allocate Lists

R Tip: Use vector(mode = "list") to Pre-Allocate Lists

Another R tip. Use vector(mode = "list") to pre-allocate lists.

result <- vector(mode = "list", 3)
print(result)
#> [[1]]
#> NULL
#> 
#> [[2]]
#> NULL
#> 
#> [[3]]
#> NULL

The above used to be critical for writing performant R code (R seems to have greatly improved incremental list growth over the years). It remains a convenient thing to know.

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