CODEWITHSUNDEEP
c#linqdictionary
sergio
sergio

Reputation: 43

Comparing difference between values in dictionary

I have a Dictionary<string, float> and want to select KeyValuePairs from that, where the difference between the float-values is smaller than a certain treshold.

This is the dictionary:

Dictionary<string, float> heights = new Dictionary<string, float> ();

sample entries:

"first", 61.456
"second", 80.567
"third", 62.456
"4", 59.988
"5", 90.34
"6", 82.123

i need those elements, with a small difference of their values, e.g. "first", "third" and "4" in a list or something similiar. the difference is a given float value, let's say 3.5

Is it possible to achieve that by Linq?

I tried to do this using loops, but it gets really messy somehow...

Upvotes: 4

Views: 648

Answers (3)

Fabjan
Fabjan

Reputation: 13676

You can create custom method that look up for close values and accepts two parameters: dictionary that holds the values and float, that is used to hold the maximum lookup range :

    static Dictionary<string, float> FindRange(Dictionary<string, float> dict, float precision)
    {
        Dictionary<string, float> temp = new Dictionary<string, float>();
        List<int> counter = new int[dict.Count].ToList(); float[] values = dict.Values.ToArray();            

        for (int i = 0; i < values.Length; i++)                            
            for (int i2 = 0; i2 < values.Length; i2++)
                if (i2 != i && Math.Abs(values[i] - values[i2]) < precision) counter[i]++;            

        for (int i = 0; i < values.Length; i++)    
           if (Math.Abs(values[i] - values[counter.IndexOf(counter.Max())]) < precision) 
               temp.Add(dict.FirstOrDefault(kv => kv.Value == values[i]).Key, values[i]);

        return temp;
    }

Example of usage :

static void Main()
{
        Dictionary<string, float> heights = new Dictionary<string, float>()
        {

            {"first", 61.456f},
            {"second", 80.567f},
            {"third", 62.456f},
            {"4", 59.988f},
            {"5", 90.34f},
            {"6", 82.123f}                
        };

        // returns max sequence of elements with difference less than 3f
        var newDict = FindRange(heights, 3f);

        foreach (var item in newDict)
        {
            Console.WriteLine(item.Key + "   "  + item.Value);
        }
}

Output : 

first 61,456
third 62,456
4     59,988

Upvotes: 1

Turbo
Turbo

Reputation: 2561

You can first sort the entries by value and then it will be easier to compare nearby entries.

var list = heights.ToList();
list.Sort((a,b) => {return a.Value.CompareTo(b.Value);});
bool first = true;
for (int i = 1; i < list.Count; ++i)
{
    if (Math.Abs(list[i-1].Value - list[i].Value) < threshold)
    {
        if (first)
        {
            first = false;
            Console.WriteLine(list[i-1]);
        }
        Console.WriteLine(list[i]);
    }
}

A working example on dotnetfiddle here.

Upvotes: 1

xan
xan

Reputation: 7568

Something like:

List<KeyValuePair<string,float>> matching = new List<KeyValuePair<string,float>>();

int i = 0;
var all = _dict.Select(kvp => kvp).ToList().OrderBy(kvp => kvp.Value);
all.ForEach(kvp => {
    if(i < all.Count() - 1 && Math.Abs(all[i+1].Value - kvp.Value) < threshhold)
    {
         matching.Add(kvp);
         if(i == all.Count() - 1) matching.add(all[i+1]); // Need to manually add the final entry if it's a match
    }
    i++;
});

Upvotes: 0

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