CSV

Common use cases and examples

Read a file all at once

Just use csv:from-file "/path/to/myfile.csv"! See from-file for more information.

Read a file one line at a time

For really big files, you may not want to store the entire file in memory, but rather just process it a line at a time. For instance, if you want to sum each of the columns of a numeric CSV file, you can do:

to-report sum-columns [ file ]
  file-open file
  set result csv:from-row file-read-line
  while [ not file-at-end? ] [
    let row csv:from-row file-read-line
    set result (map [ [ [col-total new-val] -> col-total + new-val] result row)
  ]
  file-close
  report result
end

You can also use this technique to…

Read a file one line per tick

Here’s an example model that reads in a file one line per tick:

globals [ data ]

to setup
  clear-all
  file-close-all % Close any files open from last run
  file-open "data.csv"
  % other setup goes here
  reset-ticks
end

to go
  if file-at-end? [ stop ]
  set data csv:from-row file-read-line
  % model update goes here
  tick
end

Write a file

Just use csv:to-file "/path/to/myfile.csv" my-data! See to-file for more information.

Primitives

Looking for the primitive reference for the CSV extension? You can find the full reference here.

Parsing CSV input to NetLogo data

csv:from-row csv:from-string csv:from-file

Formatting NetLogo data as CSV

csv:to-row csv:to-string csv:to-file

All Primitives

csv:from-row

csv:from-row netlogostring csv:from-row netlogostring delimiter

Parses the given string as though it were a row from a CSV file and returns it as a list of values. For example:

observer> show csv:from-row "one,two,three"
observer: ["one" "two" "three"]

Quotes can be used when items contain commas:

observer> show csv:from-row "there's,a,comma,\"in,here\""
observer: ["there's" "a" "comma" "in,here"]

You can put two quotes in a row to put an actual quote in an entry. If the entry is not quoted, you can just use one quote:

observer> foreach (csv:from-row "he said \"hi there\",\"afterwards, she said \"\"hello\"\"\"") print
he said "hi there"
afterwards, she said "hello"

Number-like-entries will be parsed as numbers:

observer> show csv:from-row "1,-2.5,1e3"
observer: [1 -2.5 1000]

true and false with any capitalization will be parsed as booleans:

observer> show csv:from-row "true,TRUE,False,falsE"
observer: [true true false false]

To use a different delimiter, you can specify a second, optional argument. Only single character delimiters are supported:

observer> show (csv:from-row "1;2;3" ";")
observer: [1 2 3]

Different types of values can be mixed freely:

observer> show csv:from-row "one,2,true"
observer: ["one" 2 true]

csv:from-string

csv:from-string netlogostring csv:from-string netlogostring delimiter

Parses a string representation of one or more CSV rows and returns it as a list of lists of values. For example:

observer> show csv:from-string "1,two,3\nfour,5,true"
observer: [[1 "two" 3] ["four" 5 true]]

csv:from-file

csv:from-file csv-file csv:from-file csv-file delimiter

Parses an entire CSV file to a list of lists of values. For example, if we have a file example.csv that contains:

1,2,3
4,5,6
7,8,9
10,11,12

Then, we get:

observer> show csv:from-file "example.csv"
observer: [[1 2 3] [4 5 6] [7 8 9] [10 11 12]]

The parser doesn’t care if the rows have different numbers of items on them. The number of items in the rows list will always be <number of delimiters> + 1, though blank lines are skipped. This makes handling files with headers quite easy. For instance, if we have header.csv that contains:

My Data
2/1/2015

Parameters:
start,stop,resolution,population,birth?
0,4,1,100,true

Data:
time,x,y
0,0,0
1,1,1
2,4,8
3,9,27

This gives:

observer> foreach csv:from-file "header.csv" show
observer: ["My Data"]
observer: ["2/1/2015"]
observer: ["Parameters:"]
observer: ["start" "stop" "resolution" "population" "birth?"]
observer: [0 4 1 100 true]
observer: ["Data:"]
observer: ["time" "x" "y"]
observer: [0 0 0]
observer: [1 1 1]
observer: [2 4 8]
observer: [3 9 27]

csv:to-row

csv:to-row netlogolist csv:to-row netlogolist delimiter

Reports the given list as a CSV row. For example:

observer> show csv:to-row ["one" 2 true]
observer: "one,2,true"

csv:to-string

csv:to-string netlogolist csv:to-string netlogolist delimiter

Reports the given list of lists as a CSV string. For example:

observer> show csv:to-string [[1 "two" 3] [4 5]]
observer: "1,two,3\n4,5"

csv:to-file

csv:to-file csv-file netlogolist csv:to-file csv-file netlogolist delimiter

Writes the given list of lists to a new CSV file. For example:

observer> csv:to-file "myfile.csv" [[1 "two" 3] [4 5]]

will result in a file myfile.csv containing:

1,two,3
4,5