Databases
StackOverflow2013
Postsdbo
POif else using the next unique value in column by key
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POif else using the next unique value in column by key
    primarykey
    data
    text
    <p>I have a question. How do I perform the following operations on the sampdata object? The result that I would like to have is the sampres object.</p> <p>Thank you.</p> <p>Pseudocode:</p> <pre><code>if sampdata[,flow[1] == flow[2], by = site_no] sampdata[,flow[2]] = next unique flow value &amp; take the corresponding gage value # if yes no change # if no </code></pre> <p>Starting data:</p> <pre><code>library(data.table) sampdata &lt;- data.table(c(02446500,02446500,02446500,02467000,02467000,02467000,06818000,06818000,06818000,06818000,06893000,06893000,06893000,06893000,06934500,06934500,06934500,07010000,07010000,07010000,07289000,07289000,07289000),c(21,21,22,70,76,82,14700,14700,14700,14800,11000,11000,11000,11100,19400,19400,19500,32000,32000,32100,146000,146000,147000),c(4,4.01,4.02,73.05,73.06,73.07,1,1.01,1.02,1.03,1,1.01,1.02,1.03,-1.2,-1.19,-1.18,-9.02,-9.01,-9,-4.43,-4.42,-4.41)) setnames(sampdata,c("site_no", "flow", "gage")) setkey(sampdata, site_no) </code></pre> <p>End result:</p> <pre><code>sampres &lt;- data.table(c(02446500,02446500,02446500,02467000,02467000,02467000,06818000,06818000,06818000,06818000,06893000,06893000,06893000,06893000,06934500,06934500,06934500,07010000,07010000,07010000,07289000,07289000,07289000),c(21,22,22,70,76,82,14700,14800,14700,14800,11000,11100,11000,11100,19400,19500,19500,32000,32100,32100,146000,147000,147000),c(4,4.02,4.02,73.05,73.06,73.07,1,1.03,1.02,1.03,1,1.03,1.02,1.03,-1.2,-1.18,-1.18,-9.02,-9,-9,-4.43,-4.41,-4.41)) setnames(sampres,c("site_no", "newflow", "newgage")) setkey(sampres, site_no) </code></pre> <p>To clarify, here are the initial data and result side-by-side, from <code>cbind(sampdata,sampres)</code>:</p> <pre><code> site_no flow gage site_no flow gage 1: 2446500 21 4.00 2446500 21 4.00 2: 2446500 21 4.01 2446500 22 4.02 3: 2446500 22 4.02 2446500 22 4.02 4: 2467000 70 73.05 2467000 70 73.05 5: 2467000 76 73.06 2467000 76 73.06 6: 2467000 82 73.07 2467000 82 73.07 7: 6818000 14700 1.00 6818000 14700 1.00 8: 6818000 14700 1.01 6818000 14800 1.03 9: 6818000 14700 1.02 6818000 14700 1.02 10: 6818000 14800 1.03 6818000 14800 1.03 11: 6893000 11000 1.00 6893000 11000 1.00 12: 6893000 11000 1.01 6893000 11100 1.03 13: 6893000 11000 1.02 6893000 11000 1.02 14: 6893000 11100 1.03 6893000 11100 1.03 15: 6934500 19400 -1.20 6934500 19400 -1.20 16: 6934500 19400 -1.19 6934500 19500 -1.18 17: 6934500 19500 -1.18 6934500 19500 -1.18 18: 7010000 32000 -9.02 7010000 32000 -9.02 19: 7010000 32000 -9.01 7010000 32100 -9.00 20: 7010000 32100 -9.00 7010000 32100 -9.00 21: 7289000 146000 -4.43 7289000 146000 -4.43 22: 7289000 146000 -4.42 7289000 147000 -4.41 23: 7289000 147000 -4.41 7289000 147000 -4.41 site_no flow gage site_no flow gage </code></pre> <p>Thank you for the edits. <s>I have added bold to the flow/gage combinations that are the same.</s> The next unique flow value and the corresponding gage value need to become the 2nd newflow/newgage values. </p> <p>This is a small set of data that I'm trying to find an automated solution for because I made those changes by hand. I'm trying to determine an automated way of making the changes since I have several thousand sites that I need to work with. Thank you.</p>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USFrank
    1. USiembry
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. COWell, it's definitely an `rle` sort of problem.
      singulars
      1. POif else using the next unique value in column by key
      1. US42-
    2. COOne thing you don't say explicitly is how "gage" changes. I guess you take the value from the same place you got the "next unique flow value"?
      singulars
      1. POif else using the next unique value in column by key
      1. USFrank
    3. CO@Frank Yes, I am taking the newgage value from the gage value where I obtained the next unique flow value. So far I have tried unique(flow), but I don't know of a way to get the corresponding gage values at those unique flow points.
      singulars
      1. POif else using the next unique value in column by key
      1. USiembry
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload