topic Re: MathScript: textscan equivalent? in LabVIEW

MathScript: textscan equivalent?

lpm4ni — Wed, 13 Jan 2010 21:12:59 GMT

To read LVM files acquired in LabView, I have been using lvm_import (http://www.mathworks.com/matlabcentral/fileexchange/19913-lvm-file-import) in MATLAB. However, I am attempting to now make use of MathScript so that all data can be acquired and analyzed in LabView, without third party software.

I am trying to modify lvm_import to account for all of the functions that MathScript does not support (structures, cell arrays, even try statements), but have run into an issue finding a replacement or workaround for textscan (http://www.mathworks.com/access/helpdesk/help/techdoc/ref/textscan.html).

Anyone with thoughts, or know of the equivalent function in MathScript? lvm_import uses fgetl to get each line in an LVM file, but I can't think of anything other than textscan to parse it the way I want. For the record, textscan is used in lvm_import by the original author.

Cheers.

Re: MathScript: textscan equivalent?

lpm4ni — Wed, 13 Jan 2010 21:20:17 GMT

Sorry, to further clarify...I know that textread exists, but I don't want to have to take the line, write it to a file, then read it back with textread. As far as I know, you cannot use textread on a string variable.

Re: MathScript: textscan equivalent?

Dennis_Knutson — Thu, 14 Jan 2010 02:04:25 GMT

Can you clarify why you aren't using the Read From Measurement File to get the data from the lvm file?

回复： MathScript: textscan equivalent?

chenyin — Thu, 14 Jan 2010 03:55:47 GMT

Maybe I know the reason why jktang do not use the vi to read the text.

For example, the text has the data just like below

12 34

54 , 34

52 456

243,32

35 5756

how to read it in LabVIEW very conveniently ? The format is so complex, because the separate will be a blank space or more.

For MATLAB,just use the function "importdata" and the data will be read quickly and accurately.

Does LabVIEW have the same function like "importdata"?

帖子被chenyin在 01-13-2010 09:55 PM

时编辑过了

Re: 回复： MathScript: textscan equivalent?

Dennis_Knutson — Thu, 14 Jan 2010 04:07:41 GMT

The lvm file was created with the Write to Measurement File and the Read From Measurement File can read it back.The file is just tab delimited text if I recall correctly and of course there are functions in LabVIEW for that. The main one being Read From Measurement File.

Of course, I don't quite understand the use of Express VIs in the first place.

Re: MathScript: textscan equivalent?

lpm4ni — Thu, 14 Jan 2010 05:51:07 GMT

Hi all, thanks for the responses. I suppose I wasn't too clear -- I need to analyze the raw data in the LVM file, not just display it. Read From Measurement File is an Express VI that I use to display the data, but in order to analyze it I need some actual algorithms.

Even if I port the output from the RFMF VI to a MathScript node, I still need to scan each line in the LVM file, delimit the contents, and analyze. I am looking more for the LabView functions to help me perform this task. While it seems simple to use any number of functions that read delimited text, further exploration into the MathScript version of them shows that NI has greatly reduced the parameterization of these functions, and there aren't any functions that parse strings with a delimiter like textscan does.

For example, textread would do the trick, except the MathScript version of it doesn't let you add parameters (i.e. a delimiter). dlmread will read from a file, but not if it contains strings (just numbers). fscanf scans it as a single string...etc.

Thank you for the responses thus far!

Re: MathScript: textscan equivalent?

Dennis_Knutson — Thu, 14 Jan 2010 07:19:08 GMT

I'm even more confused. The output of the Read From Measurement File is a dynamic data type - not text. The dynamic data can be split into the different channels or converted to waveform data types which are cluster of to, dt, and y array. All of this informaton can be processed directly by a Mathscript node without having to read the file. There are hundreds/thousands of beginning users that analyze dynamic data with Express VIs.

Re: MathScript: textscan equivalent?

lpm4ni — Fri, 15 Jan 2010 07:43:25 GMT

I'm not sure I can clarify any more, so perhaps I should work on joining the hundreds/thousands. Thanks for the reply.

Message Edited by jktang on 01-14-2010 11:43 PM

Re: MathScript: textscan equivalent?

NAKeel — Fri, 15 Jan 2010 19:58:39 GMT

I don't want to put words into Dennis's mouth, but what I think he is trying to say is that parsing the LVM file shouldn't be necessary. You can use the Convert from Dynamic Data VI to get the numeric data from the Read From Measurement File VI in a variety of formats. No parsing necessary. You can then use that data, which is now double, waveform, or a variety of other types (you can choose how you want to view it) and put that into your MathScript node directly. If I need to clarify that statement please let me know. I hope this helps.

Re: MathScript: textscan equivalent?

Dennis_Knutson — Fri, 15 Jan 2010 22:26:39 GMT

Nick,

You can put whatever words you want in my mouth. They were much more polite than the words I wanted to use.

Re: MathScript: textscan equivalent?

EngrStudent — Mon, 08 Sep 2014 15:08:39 GMT

There is a real problem with asking "why" in this context.

That is an existing MathWorks customer trying to switch their (money-producing) product to your infrastructure. Don't criticize them for it. Don't make it harder for them to do so. Dumb companies shoot themselves in the customer. Smart companies make switching to their product as painless as possible.
There is (in my case) a huge and elaborate (and butt-ugly) infrastructure that my little piece has to fit into. I wrote it in MatLab because I can do it in about a tenth of the time as LV - a reflection on my skillset and background, not necessarily your software. I am trying to convert it to MathScript and there are some "missing functions". In final production I will be passed the values from upstream, but I don't have those values right now. I am trying with my expertise to make as realistic as possible the inputs to my code. The "just import from a VI" isn't on the menu for my code. For you to assume that it is reflects your profound ignorance of my particular situation, both in terms of my skills, and in terms of the ecosystem in which I must perform.
Unless someone gets angry and works very hard, the engineer (not notoroiusly good non-technical communicators) is going to shut up and go back to their own thing. Folks inside your "club" might pat themselves on the back but new folks trying to enter the community are going to see something like this and it will look like Vlad the Impalers warniing - flee or this will happen to you too. People like me see this as you enforcing a closed community. Not only did you chase that one guy away, you have chased and are chasing others away. I'm just angry enough about it to say something before I move on.

Re: MathScript: textscan equivalent? (part 2)

EngrStudent — Mon, 08 Sep 2014 15:48:57 GMT

Dear original asker,

I'm a MatLab guy learning LabVIEW MathScript (MS) myself. Don't let the trolls get you down, there are plenty of things to commend LV. It is compiled, not interpreted, and it integrates with a very nice tool.

You have to build your own parser, like I did.

Let's say that your input file is heterogenous, and not just numeric. Reading it as a CSV will have MS dropping non-numbers. That isn't any good if you have heterogenous data - the primary purpose of using CSV in the first place.

Let's say that a typical line in your CSV looks like this:

A,1,James Truchard,16156541,1976-01-01,Austin Texas

If you use the "fread_csv" then you might get an array like this:

[0,1,0,16156541,0,0]

Nobody at LabVIEW wants to imply that James Truchard is a zero, and neither would you.

You can use fgetline to read it in from the text file. (link)

fid = fopen('foo.csv','r')

tline = getline(fid)

fclose(fid)

Now that you have the text, what can you do to split it off into chunks? MatLab used to have textscan, but found that building a (slightly) faster version was something their customers wanted - they have "strsplit" and introduced it in 2012. Strsplit takes in a string and a delimiter, and outputs a cell array of the delimited strings.

The approach is:

Find indices of the delimiters
Iterate through indices splitting out and putting into cells

Here is my code to that effect

%assumed result of fgetline

mystr ='A,1,James Truchard,16156541,1976-01-01,Austin Texas'

%make vector of indices prepadded with a single zero

myidx = [0,strfindall(mystr,',')]

%determine loop size
n = length(myidx)

%iterate through loop

for i=2:n
out(i-1)={mystr(myidx(i-1)+1:myidx(i)-1)};
end

%and prove that it works.

out{3}

%or

fprintf('%s\n',out{3})

At this point you can do what you need to in the way of conversions to numbers, dates, or such.

Re: MathScript: textscan equivalent?

EngrStudent — Mon, 08 Sep 2014 15:58:58 GMT

You do know that your post is the first that comes up in google search for "textscan mathscript" and that it has ~1000 views. The only people who search for that phrase are going to be matlab users trying to use MathScript.

How many of those are lost recurring engineering customers of LabVIEW? At $5000 per license per year, that would be a cost of $5 million per year of lost gross revenue to National Instruments, recurring for the expected adoption period (typically measured in decades).

The only argument you can make is that you did not necessarily lose all of them. The problem with that is you also can't say that you didn't lose any of them.

You did not only lose them, you lost their downstream conversions. In retail they say that one unhappy customer is 64 lost sales. Given how engineers are such divas (link), it is arguable that the multiplication factor here is substantially larger. Not only are they likely to discourage associates, they are going to influence suppliers AND customers.

Re: re: MathScript: textscan equivalent?

EngrStudent — Thu, 11 Sep 2014 16:50:37 GMT

You might also consider the "strread" function. It looks a lot like textscan.

http://zone.ni.com/reference/en-XX/help/371361G-01/lvtextmath/msfunc_strread/