Jesus Dapena

10-27-1996, 11:52 PM

Dear Biomch-L readers:

Ton van den Bogert and Juan Vicente Dura have pointed out that I

should use Mode 3 (and NOT Mode 1) in Woltring's programs if I am providing

the desired average squared deviation in VAL. I have now done this, but

there still is a problem:

Running my data with Mode=3 and with VAL=0.000010, the sum of

squares came out to be ssq = .000066 which is now small, much smaller than

the goal of: (42*0.000010=) 0.000420. So now the program is being far too

conservative, and does not smooth as much as I wanted. It is not that the

data are already so smooth (with the ssq of 0.000066) that no further

smoothing is possible under quintic spline. I think this is clear from the

results that I obtained when I tried a much larger value of VAL (0.001).

Then, I got ssq = .006823, which is a lot larger than when I tried

VAL=0.000010. This seems to indicate that the smoothing was far from

"saturated" when I used VAL=0.000010, and therefore with that value of VAL

the program should have smoothed more, getting nearer to the requested ssq

value of 0.000420.

In sum, the problem now is the reverse from when I posted my

previous message: The Woltring subroutines are not smoothing the data

enough; the sum of squares of the residuals is way below what I requested in

my input parameter (VAL). While technically this does not go against the

requirement that the sum of squares of the deviations be smaller than N*VAL,

it goes too far in the opposite direction, leaving the data too unsmooth.

Is this a standard occurrence when using Mode 3 with Woltring's

programs?

(For a long time, I have used a quintic spline program devised by

Les Jennings, and with these same data and the requested average squared

deviation set at 0.000010 the Jennings program smooths the data until a sum

of squares of 0.000420 is reached. The problem with the Jennings program is

that in the computer that I regularly use, sometimes it does not return ANY

values! So for most data sets the Jennings program is fine, but with some

it gives me trouble. That is the reason why I am checking out Woltring's

quintic spline, but up to here I am not happy with the results.)

Jesus

---

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

Ton van den Bogert and Juan Vicente Dura have pointed out that I

should use Mode 3 (and NOT Mode 1) in Woltring's programs if I am providing

the desired average squared deviation in VAL. I have now done this, but

there still is a problem:

Running my data with Mode=3 and with VAL=0.000010, the sum of

squares came out to be ssq = .000066 which is now small, much smaller than

the goal of: (42*0.000010=) 0.000420. So now the program is being far too

conservative, and does not smooth as much as I wanted. It is not that the

data are already so smooth (with the ssq of 0.000066) that no further

smoothing is possible under quintic spline. I think this is clear from the

results that I obtained when I tried a much larger value of VAL (0.001).

Then, I got ssq = .006823, which is a lot larger than when I tried

VAL=0.000010. This seems to indicate that the smoothing was far from

"saturated" when I used VAL=0.000010, and therefore with that value of VAL

the program should have smoothed more, getting nearer to the requested ssq

value of 0.000420.

In sum, the problem now is the reverse from when I posted my

previous message: The Woltring subroutines are not smoothing the data

enough; the sum of squares of the residuals is way below what I requested in

my input parameter (VAL). While technically this does not go against the

requirement that the sum of squares of the deviations be smaller than N*VAL,

it goes too far in the opposite direction, leaving the data too unsmooth.

Is this a standard occurrence when using Mode 3 with Woltring's

programs?

(For a long time, I have used a quintic spline program devised by

Les Jennings, and with these same data and the requested average squared

deviation set at 0.000010 the Jennings program smooths the data until a sum

of squares of 0.000420 is reached. The problem with the Jennings program is

that in the computer that I regularly use, sometimes it does not return ANY

values! So for most data sets the Jennings program is fine, but with some

it gives me trouble. That is the reason why I am checking out Woltring's

quintic spline, but up to here I am not happy with the results.)

Jesus

---

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