I am trying to get values of a piecewise function of linearly spaced time points from an existing data set of times and positions. so if the dataset has time values of ts= 0,5,10,15 etc and I want them spaced at twant= 0,3,6,9 etc. the twant= 0,3 would have the xs value of 0, and 6,9 would have the xs value of 5, and so on and so forth. But I cannot get it to work, the code I have below would only give the correct values if ts =0,1,2,3,4 etc. what can I do to do this? like this

'''

ts = [0,5,10,15,20,25]

twant=[0,3,6,9,12,15]

xs= [1000,2000,3000,4000,5000,6000]

def getdata(tvalue, ts, xs):

    xvals=[]
    for i in tvalue:
        for j in xs:
            if j == i:
                xvals.append(xs[j])
return xvals

getdata(twant, ts, xs)  

Output --> (1000,4000)