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Never mind,
It was the players ID that I needed not that for the cdromplayer
Jan
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I'm hesitant to ask this question since I may not understand the answer. My VB.NET (2008) skills are weak and my use of LINQ has so far been non-existent. I believe that I could get the result I want using other methods than LINQ, but this may be an opportunity for me to learn it a bit.
I have a List(Of Integer) that holds a bunch of numbers that represent durations of events in milliseconds. I need to generate a frequency table from these durations. For example, the list (usually containing about 500 elements) might be:
67, 85, 110, 112, 83, 130, 99, 105
And I might want a frequency table that looks something like this:
Duration --> Count
61-80 --> 1
81-100 --> 3
101-120 --> 3
121-140 --> 1
Here, the BinSize is 20, but this would be a user-specified value, so I don't know what my "bins" are at design-time. Also, the MaxDur might be 140 in this example, but that is also a user-specified value, so I don't know how many bins there will be at design-time. (The minimum will always be 1, so there should also be bins above for 1-20, 21-40, and 41-60 which have counts of 0).
I think it would be most useful to store the results in a Dictionary(Of Integer, Integer) where the key is the upper limit of the bin (20, 40, 60, 80, 100, 120, and 140 in this example) and the value is the counts.
Consider the following code (I'm writing off of the top of my head here):
Sub TheCaller()
'Assume we have a exampleData = List(Of Integer) with the above 8 elements
Dim count As Integer = GetFrequencies(exampleData)
End Sub
Function GetFrequencies(data As List(Of Integer)) As Integer
Return (From i In data Where i>60 And i<=80).Count()
End Function
I'm not sure I'm right, but would this return the frequency count of bin 61 to 80 milliseconds? I presume I could make 61 and 80 variables and send those as parameters to the function, but what I really want to learn how to do is generate a single function that returns a Dictionary(Of Integer, Integer) with the entire table generated. I'm thinking this requires a Group By clause. I've seen examples out there of frequency tables for a known category (e.g., count the number of orders from a particular company or the number of times a particular word appears), but I'm struggling with the fact that the number and size of my categories would be unknown.
Thanks in advance for any leads.
EDIT: In fact, I think I've got a good compromise working now. I have the caller running a Do... Loop Until iteration, retrieving the Count each time from the GetFrequencies function, which is called in the Add method of a Dictionary(Of Integer, Integer) instance. It's working well.
However, I'm still intrigued by the method ToDictionary of Enumerable. I think there is probably a more efficient (or at least concisely written) way to do this, but I'm not sure.
modified on Saturday, June 25, 2011 3:07 PM
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How do I add a reference at runtime ?
thanks!
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You can't; if you want something from an assembly without referencing it, you'll have to load it dynamic. You'd have to dig into the subject called "Reflection" to use the classes in that assembly.
Bastard Programmer from Hell 
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Hi all,
We are working on a financial project which uses excel sheets extensively.
Instead of entering values into an excel sheet, we thought of using Visual Basic to create a front end form to input values(basically numerical values) which will get stored in specific cells of a excel sheet..
we wish to keep the excel sheets as a backend datasource and just have a front end form ..
using these inputted values .. the results( charts ) will get generated as it is getting generated currently .. at a later stage we also wish to plot the charts on VB forms ..
we are unsure as to which versions of VB and excel are compatible .. what drivers to use .. and how to proceed on this task ..
I hope i was able to put across my project details .. if any doubts please let me know..
Please guide,
Thanks..
Gauti..
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Consider this ...
How about storing the data in a database like SQL-Server and use Excel for your charts and graphs ? Excel can access SQL datasources and you won't be tied so tightly.
Keep your data in a database and use whatever presentation / reporting system you like.
Keep these issues in mind:
1) backup
2) sharing data accross multiple users
3) performance / scalability
Take some time to consider this approach.
Good luck. 
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Thank you David.. this is great and exciting ..
We wish to keep excel sheets completely in the background.. i.e. we don't want to keep these excel sheets open while this application is running .. will the values stored in the database be automatically updated in the excel sheets ..??
I connected excel sheet and mysql database using the data->connection option .. but i am not sure if the values will get automatically updated without the excel sheets been kept open ..
Please suggest..
Thanks,
Gauti
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If I understand you correctly, you will need to perform something like "Refresh Data" to keep the Excel document current with the most recent data.
You might be able to configure Excel to get a fresh copy of the data each time the sheet is opened.
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thank you david..
yes .. that setting can be made .. but while running the application we don't want to keep the excel sheets open at all ..
we were thinking if some executable be made (windows forms application) in which a user enters numerical values and these values gets stored at the desired cells of the sheet .. which is stored at location say 'C:\FinExcel.xls' .. the results that are generated because of the user inputted values are later pulled out and showed on another form in the form of charts
we are just beginning to understand these languages/software .. We may be over enthusiastic for the whole process but we hope that you would understand us. ..
thanks
gauti..
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Unless you have a completely ancient version of Excel, they all allow this sort of thing.
Certainly 2003 onwards can handle.
Check here[^]
------------------------------------
I will never again mention that I was the poster of the One Millionth Lounge Post, nor that it was complete drivel. Dalek Dave
CCC Link[ ^]
Trolls[ ^]
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Thank you Dalek .. that was a good note ..
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Hi,
we made a small Windows application to input values into specific cells of our financial excel sheet ..
we used Visual Studio 2008 and MS Excel 2003 version
Now our task is to to plot the results in the form of charts on VB forms when we click on a 'Result button'
Please guide as to how this can be accomplished ..
Thanks,
Gauti.
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Weaning financial people off Excel is bloody impossible, dammed thing is too useful to them.
Take a look at SpreasSheetGear, there should be a link to them from this site, they are advertisers here. SSG will allow you to embed an excel like form into your app, the cells can be mapped to a data table and the UI is very excel like.
Never underestimate the power of human stupidity
RAH
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thanks for sharing the information Mycroft ..!!
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As one of them there 'Financial People', I concur.
There is nothing better available, and it can do just about everything I need, automating a lot of it.
------------------------------------
I will never again mention that I was the poster of the One Millionth Lounge Post, nor that it was complete drivel. Dalek Dave
CCC Link[ ^]
Trolls[ ^]
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I am a hobbyist programmer, and this may be a newbie question that has been asked before, but I was unsuccessful searching through the forums.
I am writing a data analysis program that reads disk files and parses the information. Each file is one "session" and each session contains many "trials". Trials are identified by a number of items (trial length, trial stimulus, etc.) and also holds data which are a bunch of integers.
So, I am building a trial class that has a number of properties, but one of those properties will be this array of integers (of unknown number). I'm wondering if I should represent that in the class as a simple array which heavily makes use of ReDim statements as the numbers are read and added to the array, or if I should instead represent them as a List(Of Integer) using the Add method to grow the collection.
This is a philosophical question, not a coding question. I'm sure I will be able to code it either way. What I don't know is whether one or the other is preferable considering performance or other issues. I understand that using a collection would be a bad idea because of boxing/unboxing issues, but I was given to believe List(Of T) does not suffer this penalty.
If List(Of Integer) is preferable, would you go on to say that one should always use generics and that arrays of values are always less preferable? Or perhaps a List(Of Integer) and an array of integers are the same under the hood?
Thanks.
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To be honest you pose some really good questions that really hit the fundamentals of .NET and their language integration. I don't really know enough to fully answer you.
One thing I can tell you though: memory reallocation is a very expensive operation, no matter what the implementation, and thus using constant ReDim's as the data is coming in is a bad idea. Probably 90% of the processing time will then be taken by the ReDim statement(s).
The List(Of T) on the other hand allocates blocks of memory at a time, so only once the block is filled does it reallocate.
I believe, but have no hard proof for this, that the utility classes .NET provides are all quite fast (in .NET relative terms, of course).
Quite possibly, using a similar system of allocated larger blocks at a time and only reallocating when a block is filled yourself with ReDim's could be a bit faster. At the very least, you'll probably avoid some function call overhead.
You've got me curious now  I'll look in to it, barring someone else being able to answer these questions before I get time :P
You could also always write your own test where you time both implementations. One test where you ReDim the array and add a random integer constantly, and the other where you use a List(Of Integer) and then checking the runtime of each on, say, 10000 or so iterations.
EDIT 1:
First test is in. Adding 100,000 integers to a list using ReDim's or List with standard capacity:
VB ReDim's: 8919.503 ms
List(Of Integer): 2.0002 ms
So, ReDim-ing as you can see is really a bad idea. I do have to note though that on 10,000 items the time is not noticeable.
EDIT 2:
Included a ReDim mimic version of List(Of T)'s implementation: doubling capacity every time we overflow. The results are in:"
VB ReDim's: 8907.5024 ms
List(Of Integer): 2.0001 ms
VB ReDim with Capacity: 2.0001 ms
The conclusion is: use List(Of Integer). There is no speed difference noticeable (not even in my test) between implementing it yourself. But List(Of T) handles a lot of things for you, has lots of extra functionality, and negates the need for manual array management = double win.
modified on Tuesday, June 21, 2011 2:01 PM
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additional to your EDIT 2:
did you also test starting with an big array (say 1.000.000) and redim to double size if overflow, and one redim at the end (to reduce to used size)? how fast would this be?
I cannot remember: What did I before google?
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I did not test that, as I didn't think from the OP that an array as large as 1,000,000 would be relevant. The ReDim would be slow if needed, but then again it won't be needed much.
Anyway, it'd be the same performance as starting with New List(Of Integer)(1000000), then using Add to add the items, and finally calling TrimExcess() on the list.
You can test all this yourself by writing a very simple test program. I used Now() to get the time before and after the operation and output the difference in milliseconds. Took me no more than 10 minutes to write the entire test program and do the tests.
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I tried to save this 10 minutes
I cannot remember: What did I before google?
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I wasn't on my own computer, so I poured all of those 10 minutes into EDIT 1 & 2 :P
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ok, i used a few minutes ... and proofed you are right.
AND i want YOUR computer *g* both ways used 3 milliseconds on my machine 
I cannot remember: What did I before google?
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Thank you for running the test and your very helpful answer.
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Read SlimList (I'm the author, but I think it's very relevant to your question). It discusses a bit about how List works. The List class basically uses an array that doubles in capacity each time capacity is reached. If you average out the time spent on each add operation, that comes to a performance of O(1) for each insert operation. Performing an array resize each time you add an item would average to O(N) for each insert operation (where N is the total number of objects inserted). Of course, you could reimplement the capacity-doubling functionality to make it O(1), but then you'd just be making List all over again. Read about big-O notation if you don't know what O(1) and O(N) mean.
Go with List. Read the above article if you want a more in-depth understanding of List (as well as an understanding of how it can theoretically be improved upon). Also, one more note: do not use SlimList. It merely demonstrates a theoretical improvement that is in practice so slow that it is not worthwile to with any real production code.
Steven St. John wrote: I understand that using a collection would be a bad idea because of boxing/unboxing issues, but I was given to believe List(Of T) does not suffer this penalty.
The word "collection" applies to both arrays and Lists. In either case, those collections will only suffer a boxing penalty if you try to store a non-reference type in a reference variable. For example, if you put an integer into a List(Of Object). However, putting an integer into a List(Of Integer) would not cause boxing.
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Thank you - your article was very informative!
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