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Linear Interpolation of CSV Columnar Data


 
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# 1  
Old 08-30-2019
Linear Interpolation of CSV Columnar Data

I am trying to perform linear interpolation on three columns in a CSV file.

When I run this code, I do not get any changes in the output (see Expected Output).

What am I doing wrong here?

Awk Code
Code:
'
    function interpolate(lat1, lon1, t1, lat2, lon2, t2,      i) {
        for (i = 1; i <= (t2 - t1); i++) {
            printf "%.2f,%.2f,%d\n",
                lat1 + i * (lat2 - lat1) / (t2 - t1),
                lon1 + i * (lon2 - lon1) / (t2 - t1),
                t1   + i
        }
    }
    NR <= 1 {print}
    NR >= 2 {interpolate(lat, lon, t, $1, $2, $3)}
    {lat = $1; lon = $2; t = $3}
' file.in.csv > file.out.csv

file.in.csv
22.70,-68.00,0
22.77,-68.13,1
22.83,-68.27,2
22.90,-68.40,3
22.97,-68.53,4
23.03,-68.67,5

Expected Output
22.70,-68.00,0
22.74,-68.07,0.5
22.77,-68.13,1
22.80,-68.20,1.5
22.83,-68.27,2
22.87,-68.34,2.5
22.90,-68.40,3
22.94,-68.47,3.5
22.97,-68.53,4
23.00,-68.60,4.5
23.03,-68.67,5
# 2  
Old 08-30-2019
try:
Code:
awk -F, '
function interpolate(lat1, lon1, t1, lat2, lon2, t2, p) {
for (i = 1; i <= (t2 - t1); i++) {
printf "%.2f,%.2f,%.1f\n",
lat1 + (t2 - t1) * (lat2 - lat1) / p,
lon1 + (t2 - t1) * (lon2 - lon1) / p,
t1 + i * (t2 - t1) / p
}
}
NR >= 2 {interpolate(lat, lon, t, $1, $2, $3, ++p); p=0;}
{lat = $1; lon = $2; t = $3; ++p}
{print}
' file.in.csv > file.out.csv


Last edited by RavinderSingh13; 02-28-2020 at 02:56 AM..
This User Gave Thanks to rdrtx1 For This Post:
# 3  
Old 08-30-2019
Thank you! This is exactly what I was looking for.

Quote:
Originally Posted by rdrtx1
try:
Code:
awk -F, '
   function interpolate(lat1, lon1, t1, lat2, lon2, t2, p) {
       for (i = 1; i <= (t2 - t1); i++) {
           printf "%.2f,%.2f,%.1f\n",
              lat1 + (t2 - t1) * (lat2 - lat1) / p,
              lon1 + (t2 - t1) * (lon2 - lon1) / p,
              t1 + i * (t2 - t1) / p
       }
   }
   NR >= 2 {interpolate(lat, lon, t, $1, $2, $3, ++p); p=0;}
   {lat = $1; lon = $2; t = $3; ++p}
   {print}
' file.in.csv > file.out.csv


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