linq - C# Method on one array (values) conditional on a second array (dates) -

i compute average or sum or method on elements in array of values(doubles) conditional on second array same length.

for instance, have sorted array dates (double[]dts) , compute average between start date (std) , end date (edd) on value array (double[]vals) (which simple , code below does).

but if want compute e.g. average of mondays in year code below doesnt work more. ideas? thanks!

public static double aggr(double[] dts, double[] vals, double std, double edd)     {         int stdindex = 0;         int eddindex = dts.length;          (int k = 0; k < dts.length; k++)         {             if (dts[k] == std)             {                 stdindex = k;             }             if (dts[k] == edd)             {                 eddindex = k;             }         }           return vals.skip(stdindex).take(eddindex-stdindex).average();     } 

thanks everybody. think answers work. here new code:

 public static double aggr(double[] dts, double[] vals, double std, double edd, string peakoffpeakbase, double sumavg)     {         double result;         if (sumavg == 1)         {              if (peakoffpeakbase=="peak")             {                     result = dts.zip(vals, (d, v) => new { d, v })                                         .where(dv =>  (dv.d >= std & dv.d < edd & datetime.fromoadate(dv.d).dayofweek != dayofweek.saturday & datetime.fromoadate(dv.d).dayofweek != dayofweek.sunday & datetime.fromoadate(dv.d).hour > 7 & datetime.fromoadate(dv.d).hour < 20))                                         .select(dv => dv.v).sum();             }              else if (peakoffpeakbase=="offpeak")             {                     result = dts.zip(vals, (d, v) => new { d, v })                                         .where(dv => (dv.d >= std & dv.d < edd & datetime.fromoadate(dv.d).dayofweek == dayofweek.saturday | datetime.fromoadate(dv.d).dayofweek == dayofweek.sunday | datetime.fromoadate(dv.d).hour < 8 | datetime.fromoadate(dv.d).hour > 19))                                         .select(dv => dv.v).sum();              }              else              {                     result = dts.zip(vals, (d, v) => new { d, v })                                        .where(dv => (dv.d >= std && dv.d < edd))                                        .select(dv => dv.v).sum();             }         }          else         {              if (peakoffpeakbase == "peak")             {                 result = dts.zip(vals, (d, v) => new { d, v })                                     .where(dv => (dv.d >= std & dv.d < edd & datetime.fromoadate(dv.d).dayofweek != dayofweek.saturday & datetime.fromoadate(dv.d).dayofweek != dayofweek.sunday & datetime.fromoadate(dv.d).hour > 7 & datetime.fromoadate(dv.d).hour < 20))                                     .select(dv => dv.v).average();             }             else if (peakoffpeakbase == "offpeak")             {                 result = dts.zip(vals, (d, v) => new { d, v })                                     .where(dv => (dv.d >= std & dv.d < edd & (datetime.fromoadate(dv.d).dayofweek == dayofweek.saturday | datetime.fromoadate(dv.d).dayofweek == dayofweek.sunday | datetime.fromoadate(dv.d).hour < 8 | datetime.fromoadate(dv.d).hour > 19)))                                     .select(dv => dv.v).average();             }             else             {                 result = dts.zip(vals, (d, v) => new { d, v })                                    .where(dv => (dv.d >= std && dv.d < edd))                                    .select(dv => dv.v).average();             }         }             return result;      } 

obviously terrible , verbose. combine answers below , write sth like:

result = dts.zip(vals, (d, v) => new { d, v })                                         .where(dv =>  (dv.d.intimerange(std,edd).isbusinesshour(peakoffpeakbase))                                         .select(dv => dv.v).customx(indicator); 

where intimerange , isbusinesshour extension methods described below , customx take argument , either average, sum or sth else. cant work. again!

you can use zip combine 2 arrays:

double result = dts.zip(vals, (d,v) => new { d, v})     .where( dv => somecondition(dv.d))     .select( dv => dv.v).average(); 

this calculates average of vals values, predicate somecondition returns true corresponding dts value.