CODEWITHSUNDEEP
lua
aJynks
aJynks

Reputation: 689

How do I count the number of times a string appears in a table of strings in Lua?

how would I go about counting the number of times a string occurs in a table?

Basically I have a table that is like, say 200 entires for example (but it is larger)... each entry has a sub entry called name.

so..

itemlist[i].name == somestring.

Now I can search and find a match pretty easy using an if statment while looping though the table...

if string.find(string.lower(itemlist[i].name), string.lower(searchString)) ~= nil then

So say I'm searching for Thomas, it will return when it finds "Thomas F Malone".

The thing is some cases there are more than one result for the search value.. for example.. say there are three different names that all start with Thomas.

At the moment it will just find the 1st occurrence of the Thomas.

So the plan is to count all the occurrences of Thomas and then output all of them... but I can not work out how to get the numeric value of how many times the result is found in the table.

TL;DR - How can I count the number of occurrences that of a string in a table?

Upvotes: 1

Views: 1414

Answers (2)

Rheza
Rheza

Reputation: 11

When you found the matching values, store them in a temporary table, e.g. table.insert(temporaryTable, value) rather than quitting the function using return. You can find below, a sample function which gathers and counts the occurence of a query string in a variable inside of a multidimensional table (or see it in action here).

--data
itemList = {
  {name = "Denny Kuhlman", id = "6688"},
  {name = "Russell Leisy", id = "3751"},
  {name = "Hilario Stermer", id = "1886"},
  {name = "Thomas Hemming", id = "9666"},
  {name = "Samuel Lafuente", id = "8232"},
  {name = "Lazaro Ashby", id = "5274"},
  {name = "Ronnie Nicosia", id = "9664"},
  {name = "Edison Seyal", id = "1344"},
  {name = "Jerald Officer", id = "9497"},
  {name = "Lupe Burdge", id = "266"},
  {name = "Stephan Iler", id = "5968"},
  {name = "Josue Stephens", id = "2128"},
  {name = "Salvador Ortmann", id = "3643"},
  {name = "Tony Ricker", id = "8799"},
  {name = "Corey Carbone", id = "6485"},
  {name = "Conrad Theberge", id = "139"},
  {name = "Arnulfo Oquendo", id = "2861"},
  {name = "Damien Balsley", id = "5572"},
  {name = "Efren Sloop", id = "7106"},
  {name = "Blair Clagon", id = "614"},
  {name = "Dario Service", id = "1411"},
  {name = "Paul Ashalintubbi", id = "3403"},
  {name = "Felix Veal", id = "1539"},
  {name = "Laurence Caskey", id = "2827"},
  {name = "Will Ranallo", id = "8463"},
  {name = "Thomas Brenner", id = "9599"},
  {name = "Claudio Hallmark", id = "6265"},
  {name = "Nolan Haslett", id = "9661"},
  {name = "Lenard Pereira", id = "5652"},
  {name = "Dusty Duer", id = "4034"},
}

--
function countStringOccurence(query, itemList)
  query = string.lower(query)

  --if query string is found, store index of the itemList in table searchResult
  local searchResult = {}
  for i, item in ipairs(itemList) do
    local name = string.lower(item.name)
    if string.find(name, query) then
      table.insert(searchResult, i)
    end
  end

  --return both the occurence count and the list of found item
  return #searchResult, searchResult
end

--execute the function
count, foundItemList = countStringOccurence("thomas", itemList)

--print results
print(count)                          --> 2

for i, index in ipairs(foundItemList) do
  print(index, itemList[index].name)  --> 4       Thomas Hemming
                                      --> 26      Thomas Brenner
end

NB: Please note that if your table/list entries might be moved around (e.g. sort), it might not be advisable to just store the array index because the references/values collected in foundItemList might become incorrect.

Upvotes: 1

Piglet
Piglet

Reputation: 28950

Just don't stop iterating over the table once you found something. Keep on going and increment a counter variable every time you find your string or put your results into a table and count its elements later.

local texts = {"a123", "b213", "a332", "d411", "a124"}
local result = {}
for i,v in ipairs(texts) do

  if string.find(v, "a") then
    table.insert(result, v)
  end

end

print(#result)

Upvotes: 0

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