I'm really new to Mahout (and Java - my boss asked me to learn them both at the same time), so the more basic the explanation the better! I'm trying to run KMeansClusterer (not Driver), which means I'll need to get a CSV (all values are doubles) to a List Vector.
I came across this explanation
Mahout: CSV to vector and running the program but I'm not really sure how to use it (I don't think it applies to me).
Can anyone help me either with the syntax for CSVVectorIterator or with whatever I'll need to get a CSV into a usable format?
Related
I'm currently in the process of performing feature selection on a fairly large dataset and decided to try out PySpark's UnivariateFeatureSelector module.
I've been able to get everything sorted out except one thing -- how on earth do you access the actual p-values that have been calculated for a given set of features? I've looked through the documentation and searched online and I'm wondering if you can't... but that seems like such a gross oversight for such this package.
thanks in advance!
When referring to the spark ml/mllib docs, they all start from a svm stored example. This is really frustrating me since there doesn't seem to be a straightforward way to go from a standard RDD[Row] or Dataframe (taken from a "table" select) to this notation without first storing it.
This is just an inconvenience when dealing with 3 features or so, but when you scale that up to lots and lots of features, it's implying you will be doing a lot of typing and searching.
I ended up with something like this: (where "train" is a random split of a dataset w/ features stored in a table)
val trainLp = train.map(row => LabeledPoint(row.getInt(0).toDouble, Vectors.dense(row(8).asInstanceOf[Int].toDouble,row(9).asInstanceOf[Int].toDouble,row(10).asInstanceOf[Int].toDouble,row(11).asInstanceOf[Int].toDouble,row(12).asInstanceOf[Int].toDouble,row(13).asInstanceOf[Int].toDouble,row(14).asInstanceOf[Int].toDouble,row(15).asInstanceOf[Int].toDouble,row(18).asInstanceOf[Int].toDouble,row(21).asInstanceOf[Int].toDouble,row(27).asInstanceOf[Int].toDouble,row(28).asInstanceOf[Int].toDouble,row(29).asInstanceOf[Int].toDouble,row(30).asInstanceOf[Int].toDouble,row(31).asInstanceOf[Double],row(32).asInstanceOf[Double],row(33).asInstanceOf[Double],row(34).asInstanceOf[Double],row(35).asInstanceOf[Double],row(36).asInstanceOf[Double],row(37).asInstanceOf[Double],row(38).asInstanceOf[Double],row(39).asInstanceOf[Double],row(40).asInstanceOf[Double],row(41).asInstanceOf[Double],row(42).asInstanceOf[Double],row(43).asInstanceOf[Double])))
This is a nightmare to maintain, since these rows tend to change pretty often.
And here I'm only in the stage of getting labeled points, I'm not even at a svm stored version of this data.
What am I missing here that could potentially save me days of misery?
EDIT:
I got one step closer to the solution using something called a vectorassembler to build up my vector
Usually, CSV files are raw, unfiltered sources of information. Often they provide the original source of information.
In order to build a model, you usually want to go through a data cleansing, data preparation, data wrangling (and maybe more "data x" wording) phase before you build your model. This phase usually takes a big piece of the model building, and usually requires exploration of data. Typically, a process of transformation and feature selection (and creation) occurs between the original data and the data that builds the model.
If your CSV files don't need any of these preliminary phases - good for you!
You can always make configuration files that can keep track of certain columns or column indexes that build your model.
If your DataFrame comes from a "select", I guess what you can do to improve legibility and maintainability is to use column names instead of index numbers.
df.select($"my_col_1", $"my_col_2", .. )
and then operate through
row.getAs[String]("my_col_1")
How can one generate CAD geometries of randomly oriented and randomly sized objects (3D)? I need to model randomly sized and randomly oriented rectangles--thousands to millions of them.
I have not yet come across any CAD tools that have =rand() functions that can be inputted into dimensions. Is one way perhaps to have a CAD program import a CSV file of these randomly generated parameter values?
In SolidWorks, you can have model parameters (dimension lengths/angles, constraints, etc.) stored in an Excel spreadsheet called a Design Table. Each row in the spreadsheet will represent a different configuration of your model, and each column a different parameter. You can use Excel's built-in capabilities or an export-capable tool of your choosing to generate the configurations according to your desired distribution. I don't recall off the top of my head the easiest way to get a large number of instances with different configurations into the same assembly, but you haven't really told us what you're trying to accomplish so I can't give you specific recommendations anyways.
If you have a specific CAD tool then you can often find documentation on the internal file format. With a little experimentation you can sometimes write a small external program that will generate the header of the CAD file and then loop thousands or millions of times generating each individual object. Finally you generate the lines needed to complete the file. That can sometimes be easier than trying to force a tool to do something the designers never expected. And this might let you use the software of your choice to generate the file.
I would suggest starting small. Use the CAD tool to create a file with two or three of your rectangles. Save and inspect the contents of the file to see that it matches your understanding of the needed format. Then try externally creating what should be the same file and verify your version is correctly accepted.
You might consider that some tool designers never expected someone to want thousands or millions of anything. I would suggest sneaking up on the problem. Try doubling the number of items, check this works as expected and then repeat this process again and again until either you successfully get to millions or until you find the CAD tool won't be able to handle this.
Given a word I want to get the list of most frequent predecessors and successors of the word in English language.
I have developed a code that does bigram analysis on any corpus ( I have used Enron email corpus) and can predict the most frequent next possible word but I want some other solution because
a) I want to check the working / accuracy of my prediction
b) Corpus or dataset based solutions fail for an unseen word
For example, given the word "excellent" I want to get the words that are most likely to come before excellent and after excellent
My question is whether any particular service or api exists for the purpose?
Any solution to this problem is bound to be a corpus-based method; you just need a bigger corpus. I'm not aware of any web service or library that is does this for you, but there are ways to obtain bigger corpora:
Google has published a huge corpus of n-grams collected from the English part of the web. It's available via the Linguistic Data Consortium (LDC), but I believe you must be an LDC member to obtain it. (Many universities are.)
If you're not an LDC member, try downloading a Wikipedia database dump (get enwiki) and training your predictor on that.
If you happen to be using Python, check out the nice set of corpora (and tools) delivered with NLTK.
As for the unseen words problem, there are ways to tackle it, e.g. by replacing all words that occur less often than some threshold by a special token like <unseen> prior to training. That will make your evaluation a bit harder.
You have got to give some more instances or context of "unseen" word so that the algorithm can make some inference.
One indirect way can be reading rest of the words in the sentences.. and looking into a dictionary for the words where those words are encountered.
In general, you cant expect the algorithm to learn and understand the inference in the first time. Think about yourself.. If you were given a new word.. how well can you make out its meaning (probably by looking into how it has been used in the sentence and how well your understanding is) but then you make an educated guess and over the period of time you understand the meaning.
I just re-read the original question and I realize the answers, mine included got off base. I think the original person just wanted to solve a simple programming problem, not look for datasets.
If you list all distinct word-pairs and count them, then you can answer your question with simple math on that list.
Of course you have to do a lot of processing to generate the list. While it's true that if the total number of distinct words is as much a 30,000 then there are a billion possible pairs, I doubt that in practice there are that many. So you can probably make a program with a huge hash table in memory (or on disk) and just count them all. If you don't need the insignificant pairs you could write a program that flushes out the less important ones periodically while scanning. Also you can segment the word list and generate pairs of a hundred words verses the rest, then the next hundred and so on, and calculate in passes.
My original answer is here I'm leaving it because it's my own related question:
I'm interested in something similar (I'm writing a entry system that suggest word completions and punctuation and I would like it to be multilingual).
I found a download page for google's ngram files, but they're not that good, they're full of scanning errors. 'i's become '1's, words run together etc. Hopefully Google has improved their scanning technology since then.
The just-download-wikipedia-unpack=it-and-strip-the-xml idea is a bust for me, I don't have a fast computer (heh, I have a choice between an atom netbook here and an android device). Imagine how long it would take me to unpack a 3 gigabytes of bz2 file becoming what? 100 of xml, then process it with beautiful soup and filters that he admits crash part way through each file and need to be restarted.
For your purpose (previous and following words) you could create a dictionary of real words and filter the ngram lists to exclude the mis-scanned words. One might hope that the scanning was good enough that you could exclude misscans by only taking the most popular words... But I saw some signs of constant mistakes.
The ngram datasets are here by the way http://books.google.com/ngrams/datasets
This site may have what you want http://www.wordfrequency.info/
I'm guessing this won't apply to 99.99% of anyone that sees this. I've been doing some Sawtooth survey programming at work and I've been needing to create a webpage that shows some aggregate data from the completed surveys. I was just wondering if anyone else has done this using the flat files that Sawtooth generates and how you went about doing it. I only know very basic Perl and the server I use does not have PHP so I'm somewhat at a loss for solutions. Anything you've got would be helpful.
Edit: The problem with offering example files is that it's more complicated. It's not a single file and it occasionally gets moved to a different file with a different format. The complexities added in there are why I ask this question.
Doesn't Sawtooth export into CSV format? There are many Perl parsers for CSV files. Just about every language has a CSV parser or two (or twelve), and MS Excel can open them directly, and they're still plaintext so you can look at them in any text editor.
I know our version of Sawtooth at work (which is admittedly very old) exports Sawtooth data into SPSS format, which can then be exported into various spreadsheet formats including CSV, if all else fails.
If you have a flat (fixed-width field) file, you can easily parse it in Perl using regular expressions or just taking substrings of each line one at a time, assuming you know the width of the fields. Your question is too general to give much better advice, sorry.
Matching the values up from a plaintext file with meta-data (variable names and labels, value labels etc.) is more complicated unless you already have the meta-data in some script-readable format. Making all of that stuff available on a web page is more complicated still. I've done it and it can be a bit of a lengthy project to roll your own. There are packages you can buy, like SDA, which will help you build a website where people can browse and download your survey data and view your codebooks.
Honestly though the easiest thing to do if you're posting statistical data on a website is get the data into SPSS or SAS or another statistics package format and post those files for download directly. Then you don't have to worry about it.