Questions about getting data, files, images etc. from various formats into a form that can be read, tranformed and manipulated by Mathematica

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11
votes
1answer
233 views

Exporting and reimporting a list of lists changes the dimensions

Could anyone explain to me what in the world is going on here and please help me in reading in dummy.dat properly? ...
14
votes
2answers
2k views

Importing a large Excel file

I'm trying to import a simple Excel file containing 94,000 rows and 52 columns of various types, mostly Reals. It's a 38-MB file. I get this super helpful error ...
6
votes
1answer
609 views

Stream CSV files

Ram limitations make import impractical for large CSV files. Is it possible to Stream CSV correctly? ...
19
votes
2answers
1k views

Extracting values from nested rules in JSON data

I have been using Mathematica to analyse some data from the StackExchange API. It is conveniently available in JSON form, which Mathematica interprets as replacement rules. However, some of the rules ...
6
votes
1answer
2k views

How to extract sample values from an imported WAV file?

Suppose I read a file with B = Import["something.wav"] Now how can I obtain a list of sample values?
14
votes
2answers
336 views

How to load thumbnail, not image?

Is there any way to import only the thumbnail of an image instead of the full image? I frequently work with lots of images and it would be nice if the contents of a directory could be quickly ...
4
votes
2answers
4k views

Importing from Excel

I'm trying to import a matrix from Excel to Mathematica. My code is: Import["desktop/stproj.xls", "xls", data, 1] The output is some weird stuff about population ...
8
votes
1answer
434 views

How to properly DumpSave & Get Global`s symbols inside packages while not touching Global context?

For efficiency reasons I prefer to use DumpSave instead of Save. For ease of access I prefer to save symbols in ...
6
votes
3answers
188 views

Organizing similar datasets using DownValues instead of Contexts

In his answer to this question, Leonid helped me find a way to programmatically generate contexts for holding sets of symbols with the same names. Perhaps a simpler way is to use ...
7
votes
1answer
143 views

Organizing similar datasets using Contexts or otherwise

I often import several long time series to analyze something about a city. When I have multiple cities, I use contexts. As a simple example, ...
15
votes
1answer
353 views

Importing Zip files

Mathematica can import zipped files automatically, but when the content of the zip file it's another zipped file, I just get the list of files in the second zip: ...
3
votes
1answer
284 views

Mathematica Import functions fails for data download from website

I am trying to download some data from a website that uses "java enabling" to tell me that I cannot download the data. Using Import[ "website...", "Data"] I get ...
11
votes
6answers
2k views

How do you skip missing data values in a data file?

In scanning through a simple imported file of weather station data, some dates have missing data. What is a test to use to check whether a datum is valid? I tried ...
11
votes
3answers
404 views

Data of badly formatted file

Similar as in this question, I have to read in data from a file (exampleFile.txt) which is not so well formatted. Unfortunately, I cannot find a solution by myself. Since it is a bit complicated to ...
14
votes
1answer
671 views

Release the web camera after using CurrentImage[]

CurrentImage[] will capture an image from the webcam. It is even possible to create a live video in the notebook using ...
49
votes
3answers
4k views

Recovering data points from an image

Unfortunately, some data can only be obtained in picture form (Japanese publications anyone?). Since this cannot be worked with, it has to be converted to a dataset that can; I was wondering whether ...
4
votes
3answers
287 views

Plotting data with exponentials

I have some data with 19000 sublists such as : {" 7.9080000e+01 1.9283193e+04"} Where the first number is the value for variable ...
3
votes
2answers
1k views

Importing .txt or .csv financial data

I am trying to import some financial data exported from Excel. You can find the relevant file here : Text File or CSV File This is what the data looks like in Excel : Using the following code to ...
9
votes
3answers
727 views

Is it possible to import dates and times directly as AbsoluteTime and by pass DateLists?

Date and time calculations are quite slow so I am exploring ways to minimize the number of calculations performed. As an example: ...
1
vote
1answer
407 views

How can I speed up image importing? [closed]

The following examples show how slow it is to load a simple GIF. Can anything be done to make it faster? System #1: Mathematica 8.0.1.0, HP notebook, Win7 64Bit, 2 x 2.4Ghz Intel Core i5, 2GB RAM, w/ ...
17
votes
2answers
378 views

Is Compress[] compatible between different Mathematica versions?

Compress[] was introduced in version 6 of Mathematica. It gives a compressed version of expressions represented as a string of ASCII characters. It preserves more ...
16
votes
2answers
509 views

How to develop an Import/Export converter for Compress[]ed data?

Mathematica has a cross platform data exchange format, WDX. Unfortunately importing or exporting large data from/to WDX is very slow. Using MX files is very fast, but they are not compatible across ...
6
votes
3answers
599 views

Efficient image Import

I have several sets of 20 images I need to import. Each time they have different categories. "Name"<>"Cat"<>"No" Electric B 1 for example. I need to create lists that contain the images ...
6
votes
1answer
274 views

Operations on online files via public URL access

I need M. to access an online public directory via some URL (fake in this case) http://example.com/images and perform operations similar to those M. can do on OS directories and files. Examples: ...