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Names attribute (#436)
* Names Attribute concept * add blank line
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‎concepts/names-attribute/.meta/config.json‎

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{
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"authors": [
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"colinleach"
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],
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"contributors": [],
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"blurb": "Adding names to vector elements can make them more convenient to work with."
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}

‎concepts/names-attribute/about.md‎

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# About
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Vectors can have named elements, which sometimes makes them more convenient to work with.
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## Creation
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There are three ways to add names to a vector.
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1) At vector creation time
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```R
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> work_days <- c(Mon = TRUE, Tue = TRUE, Wed = TRUE, Thu = TRUE, Fri = TRUE, Sat = FALSE, Sun = FALSE)
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> work_days
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Mon Tue Wed Thu Fri Sat Sun
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TRUE TRUE TRUE TRUE TRUE FALSE FALSE
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```
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2) By assigning a character vector to [`names()`][ref-names]
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```R
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> months <- c(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31)
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> names(months) <- month.abb
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> months
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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
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31 28 31 30 31 30 31 31 30 31 30 31
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```
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3) With [`setNames()`][ref-setnames]
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```R
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> months <- c(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31)
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> setNames(months, month.name)
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January February March April May June July August September October November December
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31 28 31 30 31 30 31 31 30 31 30 31
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```
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## Removal
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If names are no longer wanted they can be removed by setting to [`NULL`][ref-null]
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```R
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> work_days
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Mon Tue Wed Thu Fri Sat Sun
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TRUE TRUE TRUE TRUE TRUE FALSE FALSE
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> names(work_days) <- NULL
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> work_days
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[1] TRUE TRUE TRUE TRUE TRUE FALSE FALSE
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```
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The [`unname()`][ref-unname] function achieves the same thing, and perhaps make your intention clearer.
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## Working with names
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The [`names()`][ref-names] function can retrieve names as well as set them.
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```R
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> names(months) <- month.abb
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> names(months)[1:3]
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[1] "Jan" "Feb" "Mar"
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```
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A name can be used in place of the position index, with quotes required in this case.
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```R
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> months[c("Jul", "Aug")]
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Jul Aug
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31 31
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```
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For such indexing to work correctly, it is best to ensure that names are unique and non-missing.
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However, R does not enforce uniqueness.
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The usual vector operations still work, and names usually will be preserved if that makes sense.
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```R
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> months[months == 30]
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Apr Jun Sep Nov
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30 30 30 30
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> sum(months)
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[1] 365 # no meaningful names possible
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```
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## More advanced topics
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Many R objects, including `vectors`, can have arbitrary attributes attached to them. The `names` attribute is just one example, though a particularly common and important one.
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In practice, names are sometimes useful for vectors but rarely essential. The `names-attribute` becomes much more important for more complex structures such as [`lists`][concept-lists] and [`dataframes`][concept-dataframes], as we shall see in future concepts.
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[ref-names]: https://www.rdocumentation.org/packages/base/versions/3.3.0/topics/names
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[ref-setnames]: https://www.rdocumentation.org/packages/stats/versions/3.5.2/topics/setNames
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[ref-unname]: https://www.rdocumentation.org/packages/base/versions/3.3.0/topics/unname
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[ref-null]: https://www.rdocumentation.org/packages/base/versions/3.6.2/topics/NULL
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[concept-lists]: https://exercism.org/tracks/r/concepts/lists
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[concept-dataframes]: https://exercism.org/tracks/r/concepts/dataframes

‎concepts/names-attribute/introduction.md‎

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# Introduction
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Vectors can have named elements, which sometimes makes them more convenient to work with.
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## Creation
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There are three ways to add names to a vector.
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1) At vector creation time
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```R
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> work_days <- c(Mon = TRUE, Tue = TRUE, Wed = TRUE, Thu = TRUE, Fri = TRUE, Sat = FALSE, Sun = FALSE)
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> work_days
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Mon Tue Wed Thu Fri Sat Sun
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TRUE TRUE TRUE TRUE TRUE FALSE FALSE
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```
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2) By assigning a character vector to `names()`
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```R
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> months <- c(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31)
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> names(months) <- month.abb
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> months
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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
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31 28 31 30 31 30 31 31 30 31 30 31
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```
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3) With `setNames()`
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```R
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> months <- c(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31)
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> setNames(months, month.name)
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January February March April May June July August September October November December
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31 28 31 30 31 30 31 31 30 31 30 31
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```
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## Removal
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If names are no longer wanted they can be removed by setting to `NULL`
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```R
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> work_days
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Mon Tue Wed Thu Fri Sat Sun
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TRUE TRUE TRUE TRUE TRUE FALSE FALSE
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> names(work_days) <- NULL
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> work_days
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[1] TRUE TRUE TRUE TRUE TRUE FALSE FALSE
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```
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The `unname()` function achieves the same thing, and may make your intention clearer.
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## Working with names
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The `names()` function can retrieve names as well as set them.
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```R
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> names(months) <- month.abb
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> names(months)[1:3]
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[1] "Jan" "Feb" "Mar"
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```
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A name can be used in place of the position index, with quotes required in this case.
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```R
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> months[c("Jul", "Aug")]
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Jul Aug
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31 31
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```
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For such indexing to work correctly, it is best to ensure that names are unique and non-missing.
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However, R does not enforce uniqueness.
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The usual vector operations still work, and names usually will be preserved if that makes sense.
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```R
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> months[months == 30]
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Apr Jun Sep Nov
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30 30 30 30
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> sum(months)
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[1] 365 # no meaningful names possible
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```

‎concepts/names-attribute/links.json‎

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[
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{
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"url": "https://adv-r.hadley.nz/vectors-chap.html#attr-names",
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"description": "Advanced R: vector names."
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},
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{
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"url": "https://design.tidyverse.org/names.html",
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"description": "Tidyverse design principles."
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}
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]

‎config.json‎

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"uuid": "f6374c07-9244-44b2-b372-3e271b0d01be",
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"slug": "nothingness",
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"name": "Nothingness"
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},
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{
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"uuid": "be04c596-32c4-497f-9f56-7d939fe7890f",
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"slug": "names-attribute",
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"name": "Names Attribute"
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}
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],
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"key_features": [

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