LabVIEW
HELP PLEASE!!!PLOTTING OF GRAPH ONE AT A TIME
Hi,hopes somebody can help.Is there a way to take the first column of values from the text file first,plot it,and then take the second column of values and then plot it,repeating this process.The VI i wrote will automatically plots all the values straightaway,in which i do not want.I have attached the picture of it.Help please anyone 
The example of text file is as follows:
0 0
0.78 0.1097616
1.74 0.2448528
0.78 0.1097616
1.74 0.2448528
Message Edited by SG_SP_OLED on 12-31-2006 10:40 PM
This should be very easy to do in LabVIEW. Currently, you graph the second column vs. the first column in an XY graph. Do you want to first graph the first column versus the row number and then the second column vs. the row number?
What should determine when the second column is graphed (OK button, elapsed time, immediately, etc.)?
Why don't you attach your real VI and a typical data file?
You code is hard to understand from the picture because you have overlapping wires, right-to-left wires, code hidden in other cases, and confusing compositions. It makes no sense at all to "open" the file (lower left of code) if you are not using the fileref anyway. It also makes no sense why you would read the path with a value property node since the actual terminal is right there (your code cannot guarantee that the path indicator receives valid data before the value property is read above. A race condition!). "Read from a spreadheet file" is a high-level file IO VI that includes opening the file.
OK, now its a bit more clear. 🙂
I don't have access to LabVIEW 7.1 at the moment, so I just show you a code picture with some comments.
- Simply confugre the Build xy raph express node not to clear between updates.
- Now feed it one point at a time in a loop, e.g. using autoindexing.
- You can use "index array" to extract columns, no need to transpose first.
- Use the original 2D array for the table, no need to reform the array and transpose.
- Your boolean buttons, case structure, and outer loop serve no real purpose. You simply spin the loop, consuming 100% of your CPU doing nothing most of the time. If you really want to start updating with a FP control, use an event structure in a loop.
- As I already said, get rid of that silly path property node and file open.
Message Edited by altenbach on 01-01-2007 10:48 AM
It's the same tool (Read from spreadsheet file) you already have placed in your VI. 🙂
(Since I opened your VI in LabVIEW 8.20, things look a bit different. The functionality is the same).
Message Edited by altenbach on 01-01-2007 08:04 PM
Well, don't break my code by making random modifications! 🙂
My code refeshes the entire table (all rows!) at once. If you want to update the table incrementally, you can use something like in the attached modification.
Note that you don't need a seperate FOR loop (especially not one with 1000 iterations!!!) because the graph update and table update are synchronous. If you autoindex at the loop boundary, you only get one row at a time, you need to incrementally rebuild the 2D array, e.g. in a shift register. You don't magically generate the full 3D array from each row by making the row into a 2D table as you tried.
Please get rid of all these unecessary transpositions. As you can see in my example, you can just process one row at a time, autoindexing a 2D array.
All clear? 🙂
Message Edited by altenbach on 01-01-2007 10:23 PM
