Jesus Dapena

10-27-1996, 10:06 AM

Dear Biomch-L readers:

I am trying to use Herman Woltring's GCVSPL and SPLDER programs to

smooth data with quintic spline. I am using these programs in "Mode 1"

(where the smoothing factor is NOT decided by the program but by the person

running the program), and I am providing a value for VAL (the smoothing

factor). As I understand it, when in Mode 1, VAL is the upper limit of the

average squared deviation between the raw and smoothed location data.

Therefore, the sum of the squares of the differences between the raw and

smoothed location data (0th derivative) must be equal or smaller than N*VAL

(where N is the number of data points).

With the data points that Woltring provides in his GCVTST test

program (Kit Vaughan's golf ball drop data), I found that this holds true.

However, when I try other data, I find that the sum of squares is much

larger than N*VAL, which should not happen.

Has anyone in Biomch-L ever encountered this problem with Woltring's

programs? At this point, I tend to think that Woltring's programs work OK,

and that I am doing something wrong, but I can't figure out what it is!

In case there is someone curious enough to check this, here are the

data that I am having trouble with:

x( 1)= 9.660D0

y( 1)= 6.494D0

x( 2)= 9.680D0

y( 2)= 6.615D0

x( 3)= 9.700D0

y( 3)= 6.719D0

x( 4)= 9.720D0

y( 4)= 6.826D0

x( 5)= 9.740D0

y( 5)= 6.921D0

x( 6)= 9.760D0

y( 6)= 7.006D0

x( 7)= 9.780D0

y( 7)= 7.088D0

x( 8)= 9.800D0

y( 8)= 7.159D0

x( 9)= 9.820D0

y( 9)= 7.220D0

x(10)= 9.840D0

y(10)= 7.273D0

x(11)= 9.860D0

y(11)= 7.325D0

x(12)= 9.880D0

y(12)= 7.387D0

x(13)= 9.900D0

y(13)= 7.478D0

x(14)= 9.920D0

y(14)= 7.615D0

x(15)= 9.940D0

y(15)= 7.769D0

x(16)= 9.960D0

y(16)= 7.944D0

x(17)= 9.980D0

y(17)= 8.091D0

x(18)= 10.000D0

y(18)= 8.181D0

x(19)= 10.020D0

y(19)= 8.259D0

x(20)= 10.040D0

y(20)= 8.318D0

x(21)= 10.060D0

y(21)= 8.361D0

x(22)= 10.080D0

y(22)= 8.420D0

x(23)= 10.100D0

y(23)= 8.510D0

x(24)= 10.120D0

y(24)= 8.577D0

x(25)= 10.140D0

y(25)= 8.643D0

x(26)= 10.160D0

y(26)= 8.710D0

x(27)= 10.180D0

y(27)= 8.771D0

x(28)= 10.200D0

y(28)= 8.817D0

x(29)= 10.220D0

y(29)= 8.867D0

x(30)= 10.240D0

y(30)= 8.923D0

x(31)= 10.260D0

y(31)= 8.982D0

x(32)= 10.280D0

y(32)= 9.073D0

x(33)= 10.340D0

y(33)= 9.352D0

x(34)= 10.400D0

y(34)= 9.488D0

x(35)= 10.460D0

y(35)= 9.764D0

x(36)= 10.520D0

y(36)= 9.883D0

x(37)= 10.580D0

y(37)= 10.036D0

x(38)= 10.640D0

y(38)= 10.243D0

x(39)= 10.700D0

y(39)= 10.419D0

x(40)= 10.760D0

y(40)= 10.651D0

x(41)= 10.820D0

y(41)= 10.738D0

x(42)= 10.880D0

y(42)= 10.872D0

With these data and a smoothing factor VAL=0.000010, I get a sum of

squares ssq= 0.112067, when the maximum value that the sum of squares

should reach is (42*0.000010=) 0.000420.

If someone in Biomch-L who is a regular user of Woltring's package

runs these data ***in Mode 1, and with VAL=0.000010***, can you please tell

me if the sum of squares that you get is (a) 0.112067 (as I am getting) or

(b) the expected value (0.000420 or less).

Jesus Dapena

---

Jesus Dapena

Department of Kinesiology

Indiana University

Bloomington, IN 47405, USA

1-812-855-8407

dapena@valeri.hper.indiana.edu

http://ezinfo.ucs.indiana.edu/~dapena

I am trying to use Herman Woltring's GCVSPL and SPLDER programs to

smooth data with quintic spline. I am using these programs in "Mode 1"

(where the smoothing factor is NOT decided by the program but by the person

running the program), and I am providing a value for VAL (the smoothing

factor). As I understand it, when in Mode 1, VAL is the upper limit of the

average squared deviation between the raw and smoothed location data.

Therefore, the sum of the squares of the differences between the raw and

smoothed location data (0th derivative) must be equal or smaller than N*VAL

(where N is the number of data points).

With the data points that Woltring provides in his GCVTST test

program (Kit Vaughan's golf ball drop data), I found that this holds true.

However, when I try other data, I find that the sum of squares is much

larger than N*VAL, which should not happen.

Has anyone in Biomch-L ever encountered this problem with Woltring's

programs? At this point, I tend to think that Woltring's programs work OK,

and that I am doing something wrong, but I can't figure out what it is!

In case there is someone curious enough to check this, here are the

data that I am having trouble with:

x( 1)= 9.660D0

y( 1)= 6.494D0

x( 2)= 9.680D0

y( 2)= 6.615D0

x( 3)= 9.700D0

y( 3)= 6.719D0

x( 4)= 9.720D0

y( 4)= 6.826D0

x( 5)= 9.740D0

y( 5)= 6.921D0

x( 6)= 9.760D0

y( 6)= 7.006D0

x( 7)= 9.780D0

y( 7)= 7.088D0

x( 8)= 9.800D0

y( 8)= 7.159D0

x( 9)= 9.820D0

y( 9)= 7.220D0

x(10)= 9.840D0

y(10)= 7.273D0

x(11)= 9.860D0

y(11)= 7.325D0

x(12)= 9.880D0

y(12)= 7.387D0

x(13)= 9.900D0

y(13)= 7.478D0

x(14)= 9.920D0

y(14)= 7.615D0

x(15)= 9.940D0

y(15)= 7.769D0

x(16)= 9.960D0

y(16)= 7.944D0

x(17)= 9.980D0

y(17)= 8.091D0

x(18)= 10.000D0

y(18)= 8.181D0

x(19)= 10.020D0

y(19)= 8.259D0

x(20)= 10.040D0

y(20)= 8.318D0

x(21)= 10.060D0

y(21)= 8.361D0

x(22)= 10.080D0

y(22)= 8.420D0

x(23)= 10.100D0

y(23)= 8.510D0

x(24)= 10.120D0

y(24)= 8.577D0

x(25)= 10.140D0

y(25)= 8.643D0

x(26)= 10.160D0

y(26)= 8.710D0

x(27)= 10.180D0

y(27)= 8.771D0

x(28)= 10.200D0

y(28)= 8.817D0

x(29)= 10.220D0

y(29)= 8.867D0

x(30)= 10.240D0

y(30)= 8.923D0

x(31)= 10.260D0

y(31)= 8.982D0

x(32)= 10.280D0

y(32)= 9.073D0

x(33)= 10.340D0

y(33)= 9.352D0

x(34)= 10.400D0

y(34)= 9.488D0

x(35)= 10.460D0

y(35)= 9.764D0

x(36)= 10.520D0

y(36)= 9.883D0

x(37)= 10.580D0

y(37)= 10.036D0

x(38)= 10.640D0

y(38)= 10.243D0

x(39)= 10.700D0

y(39)= 10.419D0

x(40)= 10.760D0

y(40)= 10.651D0

x(41)= 10.820D0

y(41)= 10.738D0

x(42)= 10.880D0

y(42)= 10.872D0

With these data and a smoothing factor VAL=0.000010, I get a sum of

squares ssq= 0.112067, when the maximum value that the sum of squares

should reach is (42*0.000010=) 0.000420.

If someone in Biomch-L who is a regular user of Woltring's package

runs these data ***in Mode 1, and with VAL=0.000010***, can you please tell

me if the sum of squares that you get is (a) 0.112067 (as I am getting) or

(b) the expected value (0.000420 or less).

Jesus Dapena

---

Jesus Dapena

Department of Kinesiology

Indiana University

Bloomington, IN 47405, USA

1-812-855-8407

dapena@valeri.hper.indiana.edu

http://ezinfo.ucs.indiana.edu/~dapena