| Author |
 Topic  |
|
|
tib
Switzerland
105 Posts |
 Posted - 01/18/2002 : 08:32:34 AM
|
I have a y-dataset which is increasing (or decreasing) with x.
Now, I want to display the data only starting from when the y-value is above a certain noise level.
The functions xindex(x,dataset) and xindex1(x,dataset) are not helpful for this task since they give me only a x-threshold. The list(value,dataset) function would be ideal, unfortunately it makes an exact comparison, so it's useless for my purpose.
Futhermore, I want to display the data of a y1-column beginning from when the value of a y2 column (they have the same x-column) is above a certain threshold.
The only way I found is to scan the columns "manually".
THR=4e-11; // threshold value;
NRW=data1!wks.maxRows; // number of rows;
loop (ii,1,NRW) {
if (data1_b[ii]>THR) {IDX=ii; break;};
};
type "The row index where the value is above $(THR) is $(ii)";
Maybe anybody knows about a better and probably faster method?
Isn't there any function like yindex(y,ydataset)?
An other question concerning xindex1(x,dataset): when I fill x columns data1_a with 1,2,3,4... and data1_b with any values and I perform the command xindex1(0,data1_b) I get back 2. But shouldn't it be 1? |
|
|
Mike Buess
USA
3037 Posts |
Posted - 01/18/2002 : 12:52:41 PM
|
This may be a little better...
tmp=(data1_b>THR)?1:0;
ii=list(1,tmp); del tmp;
type "The row index where the value is above $(THR) is $(ii)";
The list() function works here because the values in tmp are exactly 0 and 1.
Mike Buess
Origin WebRing Member |
 |
|
|
tib
Switzerland
105 Posts |
Posted - 01/23/2002 : 05:06:06 AM
|
Mike, this structure is really good!
Both functions are in the manual. But I would like to see more of such combinations as examples there. I thought that finding thresholds and limits are daily tasks that there even should be a single function for it.
1. search for the first number: value > THR
TMP=(Data1_B>THR)?1:0;
LOW=list(1,TMP);
a) the first number > THR is at row index 50
b) all numbers > THR
c) no number > THR
The results of your formula are:
1a) LOW=50
1b) LOW=1
1c) LOW=0
All these results are OK.
With this, I could limit a dataset by set Data1_B -b LOW;
But!
2. search for the last number: value < THR
TMP=(Data1_B < THR)?1:0;
HIG=list(0,TMP);
a) the last number < THR is at row index 50
b) all numbers < THR
c) no number < THR
The results of your formula are:
2a) HIG=51 50 would be right
2b) HIG=0 last index of last row would be nice
2c) HIG=1 0 would be nice;
I want to set the end range of the dataset by set Data1_B -e HIG;
In that case a have to add a sequence:
HIG-=1; // subtract 1;
if (HIG==-1) {get Data1_B -e AAA; HIG=AAA};
That should work. But maybe you also have a better solution for that?
Thanks a lot! Tilman.
By the way, do you know if there is a command for resetting the dataset to full range?
AAA=Data1!wks.maxRows; set Data1_B -e AAA; |
|
|
|
Mike Buess
USA
3037 Posts |
Posted - 01/23/2002 : 09:57:09 AM
|
Hi Tilman,
Actually, there is a built-in Origin function called "tReplace" that seems suited for this sort of thing. I have never used it, but according to its help file description it should work for you. Search for it in LabTalk help.
Note: This function was introduced in Patch 2 for Origin 6.1 and more documentation is available in the release notes. Those notes say that it is much faster than the ternary operator method that I suggested.
Mike Buess
Origin WebRing Member
Edited by - Mike Buess on 01/23/2002 13:59:19 |
|
|
| |
Topic |
|
|
|
Finding a threshold value