Bash arrays: rebin/interpolate smaller array to large array


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# 1  
Bash arrays: rebin/interpolate smaller array to large array

hello,
i need a bit of help on how to do this effectively in bash without a lot of extra looping or massive switch/case

i have a long array of M elements and a short array of N elements, so M > N always. M is not a multiple of N.

for case 1, I want to stretch N to fit M
arrayHuge
Code:
 H = ( [0]....          [M-1] ) has M elements

arraySmall
Code:
 S= ( [0]....          [N-1] )  has N elements

arraySmallRemapped
Code:
S_expanded= ( S[0] ....    S[N-1]%2 .....      S[N-1])  has M elements

i can do this by checking the remainder with switch/case of if/then but am looking for a better way.
this code works
Code:
  for (( i=1; i<${LengthM}+1; i++ ));
  do
    case $(( ($i*$arraySmall/$arrayHuge ) )) in
    0) tmp="$arraySmall[0]";;
    1) tmp="$arraySmall[1]";;
    N-1]) tmp="$arraySmall[N-1]";;
    *)tmp="$tmp";;
   esac
  S_expanded[$i]="$tmp"
 done


Last edited by f77hack; 02-13-2016 at 05:52 PM.. Reason: corrected loop
# 2  
Not too clear what you expect. How about
Code:
S=(0 1 2 3)
H=(A B C D E F G H I J K)
while [ ${#SX[@]} -lt ${#H[@]} ]; do SX=(${SX[@]} ${S[@]}); done
for ((i=${#H[@]}; i<=${#SX[@]}; i++)); do unset SX[$i]; done
echo ${SX[@]}, ${#SX[@]}, ${!SX[@]}, ${H[@]} 
0 1 2 3 0 1 2 3 0 1 2, 11, 0 1 2 3 4 5 6 7 8 9 10, A B C D E F G H I J K

This User Gave Thanks to RudiC For This Post:
# 3  
Quote:
Originally Posted by RudiC
Not too clear what you expect. How about
Code:
S=(0 1 2 3)
H=(A B C D E F G H I J K)
while [ ${#SX[@]} -lt ${#H[@]} ]; do SX=(${SX[@]} ${S[@]}); done
for ((i=${#H[@]}; i<=${#SX[@]}; i++)); do unset SX[$i]; done
echo ${SX[@]}, ${#SX[@]}, ${!SX[@]}, ${H[@]} 
0 1 2 3 0 1 2 3 0 1 2, 11, 0 1 2 3 4 5 6 7 8 9 10, A B C D E F G H I J K

Great. Didn't think of wrapping the small array like that. I knew someone would come up with good compact code. Thanks!

This is what I was looking for

Code:
while [ ${#SX[@]} -lt ${#H[@]} ]; do SX=(${SX[@]} ${S[@]}); done


Last edited by f77hack; 02-13-2016 at 06:52 PM.. Reason: added code
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