Questions tagged [streams]
A source of input or output: files and pipes are both examples of general Mathematica objects known as streams.
87
questions
3
votes
2answers
103 views
How do I import a 1 gig text file by only importing the last 3 lines of every 10 line chunk?
I am trying to get the last three lines of every 10 line chunk into mathematica as a data variable. The text file has 3 columns. For example:
...
2
votes
1answer
41 views
1
vote
1answer
41 views
write output to stream and also print it
I tried to save the Print[] output to a file using this code:
...
2
votes
0answers
61 views
0
votes
0answers
30 views
Selective read/write on a mx file
Consider an mx file to which has been saved the following data
...
4
votes
0answers
29 views
Is there an equivalent to “Open Update”
I'm writing a binary file that contains a header followed by the data.
The header contains the length of the data.
The data is written first, skipping past the header.
Once done, I would like to ...
3
votes
0answers
85 views
Reading through file one line at a time, running out of RAM [closed]
I have a handful of files (some of which are very large), and I would like to loop through them one line at a time, run a calculation, and then write the result of the calculation to a new output file:...
1
vote
0answers
45 views
Issue with StreamDensityPlot
I'm plotting a complicated vector field that is yielding the following particular StreamDensityPlot. I'm using the following command to plot it:
...
5
votes
1answer
123 views
How do I reliably read from stdin using wolframscript?
I am trying to direct a stream of data to a wls script in a command line environment. Wolframscript provides the ...
2
votes
1answer
147 views
Vector field Stream?
The following graph shows the vector plot. How can I plot the solid lines which represents how the vectors are spatially varying and both on the same graph (vector plot and stream field)?
...
10
votes
1answer
2k views
5
votes
0answers
129 views
Optimize Use of PeakDetect in Mathematica
I am quite new to Mathematica and I am looking for some advice in order to improve and optimize my code.
Here is what I am trying to do:
Open a stream
Read the stream line by line and store it in "...
1
vote
2answers
92 views
Reading CSV data from a stream [duplicate]
I'm trying to figure out how many rows/records my csv file has, which I have to stream because it's quite large.
Can someone tell me if my approach works and how I can get it to loop through the ...
2
votes
0answers
171 views
How to force Close of opened stream when stream write previously failed (bug in opening stream twice)?
I opened a stream like:
str = OpenWrite[NotebookDirectory[] <> "myStream.tsv"];
and made an error when writing the first line (meant to be the tsv headers):...
9
votes
2answers
110 views
What is the fastest way to read the new lines in the dynamically updatable file?
I'm writing a log to a simple .txt file and want to read the last few records using Mathematica. But there are some problems.
f = OpenRead["logs.txt"];
Skip[f, ConstantArray[Number, 2], 1];
Read[f, ...
2
votes
1answer
123 views
Streams in parallel kernels. Writing in multiple files in ParallelDo loop in Mathematica
I need to write data in multiple files in ParallelDo loop:
...
2
votes
2answers
49 views
Naming indexed output streams
I need to write into multiple files in a Do loop.
Hence, I tried to open multiple streams:
...
3
votes
2answers
168 views
Join two datasets with a function similar to Vlookup [Big Dataset and Efficiency issue] - Wizards are welcome!
I am working on a huge dataset and I have a lot of data formatted in XML, we are talking about a couple of GBs. For this reason I am currently using the stream function to read them and extract the ...
2
votes
0answers
69 views
Why does ReadString complain about the stream not being opened in binary format?
This works fine:
...
11
votes
0answers
117 views
LibraryLink: How to read from a Mathematica stream in C?
Mathematica has a flexible streams interface. Functions like Read can read from a "stream" that may be backed by a file, pipe, string, network resource, etc. We can ...
3
votes
1answer
286 views
How many records? In a file (streaming)
I want to know how many records a file (large data) contains...
with streaming...like this:
...
7
votes
0answers
450 views
Communicating with server over Websocket using SocketConnect
I am trying to connect to a web socket feed of Gdax. The documentation is here, https://docs.gdax.com/#websocket-feed. There is no account needed and the information is public. I have successfully ...
0
votes
0answers
86 views
Is it possible to parallelize reading in Mathematica?
I have a gigantic data file that needs to be processed. I am reading it in chunks using ReadList with an InputStream. In my ...
3
votes
2answers
93 views
Explicitly control newline behaviour when writing strings with arbitary encoding
On Windows system, Mathematica by default opens stream which will automatically transform any "\n" into "\r\n". But I want pure ...
19
votes
1answer
368 views
Is building an event-based parser possible/reasonable in Mathematica (WL)?
Too long? Go to Problems section
Background
I like to learn by doing small, sometimes artificial, projects. Among other things I had 'parsers', and 'stream methods / streams in MMA' on my to learn ...
5
votes
1answer
381 views
Matrix Vector multiplication for very big matrices (>>RAM)
Problem
Suppose a matrix-vector product of the form $M\vec{v}$ should be calculated where the amount of storage needed to store $M$ is noticeably larger than the available RAM on a machine. What is ...
1
vote
0answers
32 views
How to export result from SQLResultSet into a csv
I have a sql query which produces very large data from a remote server but the data is too large to fit into memory all at once. So i want to read and export it sequentially into a csv. I am using the ...
1
vote
1answer
36 views
Read not advancing StreamPosition [closed]
[MMA 11.0, Win7 64bit]
I have a number of CVS files of ~1-2GB, millions of rows, so I want to read them in records, chunks building on Albert Retey's answer to this question
I assumed, and the ...
5
votes
0answers
62 views
Why ReadList ignores NullRecords for Number?
When thinking on this recent question the immediately obvious solution which came to my mind was to use ReadList with options ...
6
votes
1answer
169 views
Is there a way to redirect the output from `Echo`?
The newish function Echo is tremendously useful in quick-and-dirty debugging, since you can stick it pretty much anywhere in an expression and get feedback about ...
3
votes
0answers
37 views
Unexpected behaviour with WordSeparators and Read [duplicate]
I am confused about how Read separates elements.
The following all work fine:
...
4
votes
1answer
55 views
How to get the standard error stream for a ProcessObject?
When you run an external program using RunProcess, the program will run to completion and you will receive an association containing the exit code, stuff that went ...
5
votes
1answer
184 views
wolframscript creates tons of log files
On Linux, wolframscript seems to create log files in .Mathematica/ApplicationData/ProcessLink/Streams
for example:
...
1
vote
0answers
95 views
Why does using BinaryWrite make my file bigger? [closed]
I have a binary file 00010005.dat. I want to normalize the matrix so I use the following code:
...
7
votes
1answer
868 views
SliceStreamPlot3D or StreamPlot3D
I know that neither of the two functions listed in the title exist, but I basically replaced vector for stream to give you an idea of what I want. The most ideal would be ...
3
votes
0answers
880 views
How to visualize the vorticity of a 3D velocity field? [closed]
I sample a snapshot from a system with 50 particles including their position and instant velocities.
The snapshot is a list of 3 position and 3 velocities values per particle. i.e. 50 lines each of ...
9
votes
2answers
280 views
Is there a way to create ZIP OutputStream ?
I want to write data to a file using compression. Is it possible to do that just in time (like in java ZipOutputStream). E.g. what I want:
...
27
votes
3answers
600 views
Can Mathematica edit large binary files in-place?
I have a very large binary data file (several hundred GB) which I would like to edit using Mathematica. The only edits required are a few isolated byte replacements—no insertions or deletions. Is it ...
3
votes
0answers
247 views
How to flush stdout stream?
I am aware that one can write to a terminal standard output like so:
WriteString["stdout","Some stuff","\r"];
Note here that I am using a carriage return on ...
4
votes
1answer
208 views
How to read *all* input from stdin?
The answers given to this similar question won't do, because those solutions read only one line from stdin.
I want to read all available lines, pretty much in the ...
4
votes
3answers
675 views
how do I to create a function similar to feof in C?
Using C language,I can use feof to test if the pointer at end of file.
while(!feof(fp))
{
//to do
}
But in the mma,I ...
3
votes
1answer
320 views
How to Terminate Read at EndOfFile
We are working on a project that reads in a stream, extracts information from it, and then needs to stop the calculation when it reaches EndOfFile.
So for example,...
6
votes
1answer
73 views
Can Read[] apply a custom function automatically to the read values?
Read[stream, Number] will return a single read number. We can use a number of standard, documented types instead of Number, ...
11
votes
0answers
446 views
How to read and write data to open socket?
I am trying to open connection with socket. I am using this:
...
1
vote
1answer
133 views
Inconsistency of WriteString
Important Note
A kernel or maybe Front End restart probably fixed the problem. I did something weird today which is evaluate Context[StringQ]="test`", perhaps that ...
3
votes
1answer
98 views
`ReadString` and `StreamPosition` behaving strangely with custom terminators
I've stumbled on a strange behavior while trying to use custom terminators for ReadString.
When I use a simple String as the ...
5
votes
1answer
115 views
How can I dynamically display a stream position?
If I create a stream,
str = StringToStream["how can I dynamically display the stream position"];
Read[str, Word]
"how"
then, when I use,
...
4
votes
1answer
358 views
Importing large datasets using streams
I work with large data sets with 22 columns and up to a million rows. Each row contains one observation with several variables. All variables are numbers.
Simplyfied example:
1, 1, 2, 3, 4, 5, 6,...
4
votes
2answers
283 views
Parsing tab delimited file
Problem Description
I have my data arranged in a tab delimited file and I'm trying to parse/access certain parts of it.
As an example, I'd like to extract the number of points and the sampling ...
2
votes
1answer
115 views
Use e notation in Stream output
I'm trying to save the results of a huge Radia calculation. I evaluate the function in a loop at multiple locations.
To export the data my first approach was to fill a Table and use the ...
