PHP remove duplicate instances of dates in an array - php

Question

I've tried various permutations of array_unique, and have searched other generic questions here on removing duplicate values from an array, but I can't quite set upon the answer I need. I have an array being passed of dates and values, and only want to view the DATE value once per date.
I'm using this for a Google chart and only want the date labels to show up once for each date. And I don't want to remove it entirely, because I want to be able to plot it on the chart.
So, an example array being passed:
["June 4",30],["June 4",35],["June 5",46],["June 5",38.33],["June 5",12]
And how I want it:
["June 4",30],["",35],["June 5",46],["",38.33],["",12]
Ideas?

Answer 1

Since you're using the data to feed into a google chart, I'm assuming that you know exactly what you need as far as output data. There's already some suggestions above for better ways to structure the data, but that probably won't work directly for a google chart.
How about this?
$data = [["June 4",30],["June 4",35],["June 5",46],["June 5",38.33],["June 5",12]];
$found = array();
foreach ($data as $i => $x) {
if (in_array($x[0], $found)) {
$data[$i][0] = '';
} else {
$found[] = $x[0];
}
}
print_r($data);
Basically, it's just building a list of dates that it's already seen. We loop through the data, and check if we've seen the date... if we have, we clear it from the data, otherwise we save it to the list so it'll be cleared next time.
Here's an alternate solution that only checks for duplicate dates that are consecutive, unlike the first solution that will remove all duplicates. This is probably closer to what you need for charting:
$data = [["June 4",30],["June 4",35],["June 5",46],["June 5",38.33],["June 5",12]];
$last = '';
foreach ($data as $i => $x) {
if ($x[0] == $last) {
$data[$i][0] = '';
} else {
$last = $x[0];
}
}
print_r($data);
In this case, we're just keeping track of the last date we've seen... and if our new date matches that, we clear it.

Answer 2

This is a possible solution for your problem, though I would recommend a re-construction as Patashu & Nikola R stated.
$untrimmed = [["June 4",30],["June 4",35],["June 5",46],["June 5",38.33],["June 5",12]];
$trimmed = stripDates($untrimmed);
function stripDates($dates) {
foreach( $dates as $key=>$date ) {
if ($key>0) {
if ($date[0] === $dates[$key-1][0]) {
$dates[$key][0] = "";
} else if($dates[$key-1][0] === "") {
for ($i = $key-1; $i > -1; $i--) {
if ($date[0] === $dates[$i][0]) $dates[$key][0] = "";
if ($dates[$key] != "") break;
}
}
}
}
return $dates;
}
// Note: This would require dates to be added chronically
//Output: ["June 4",30],["",35],["June 5",46],["",38.33],["",12]
I would recommend something like this:
$unconstructed = [["June 4",30],["June 4",35],["June 5",46],["June 5",38.33],["June 5",12]];
$constructed = constructAssoc($unconstructed);
function constructAssoc($dates) {
$constructed = array();
foreach( $dates as $index=>$date ) {
if (!array_key_exists($date[0], $constructed)) {
$constructed[$date[0]] = array("index"=>$index, "value"=>$date[1]);
} else {
array_push($constructed[$date[0], ["index"=>$index,"value"=>$date[1]]);
}
}
return $constructed;
}
//Output: ["June 4"=> [["index"=>0, "value"=>30], ["index"=>1, "value"=>35]], "June 5"=>[["index"=>2, "value"=>46], ["index"=>3, "value"=>38.33], ["index"=>4, "value"=>12]]]
Note: Added index in recommended solution if a more accurate re-construction is needed.