Suppose G is a (large) two-dimensional array.
If I save the array by writing G to a text file as in:
WRITE(1,*) G
and then later in a separate subroutine I try to recover by doing this:
READ (1,*) G
Will the READ statement keep reading all the lines of the text file until G is filled up with values?
Basically, how "smart" is this read statement in this context?
Yes. A list directed read statement will continue reading records until it has satisfied the list of input items or run out of file.
Related
I have a text file (5 columns "\t" separated) that's being written to by another software. I need to take the readings from the file and do some calculations. Is there a was to read the new lines added to the file and process it then repeat again for every new set of lines. I don't mind a bit of delay as long as it does the job.
My idea is to start reading the file line by line until the end of file, then it will read from where it stopped last until the new end of file ...etc.
Can this be done in Matlab? Can I specify the starting line for the file reading? can I also update the end of file point?
To prevent the loop from breaking at the eof point, I think I should set my loop to be controlled by time or anything else, while it should check for eof at the end of every iteration.
I've mostly worked with Matlab, but if there is a better option to use for this purpose (that I can reasonably learn) please feel free to guide me.
Edit1: I've tried using dlmread as you suggested, when I read the file outside the loop it reads the file correctly even when I change R1 and with the other software updating the text. However, when I put it in a loop I get this error:
Error using dlmread (line 143)
Empty format string is not supported at the end of a file.
Here is my code to read it multiple times:
clear all
x=0;
R1=0; C1=0;
while(x<10)
M = dlmread('tst_4.txt','\t',R1,C1);
R1=length(M);
x=x+1;
end
Thanks
You can used dlmread(filename,delimiter,R1,C1). Where R1 and C1 are the row and column offset respectively. By setting the row offset to the last row that you have read, you can read the file content excluding what you would have already read.
I am using Matlab 2013b. I have a list of excel files in a directory and I want to open chosen ones within a loop to read out the data.
I only know the start of each of the file names however, not the ending. I have a vector of numbers that provide the identifying portion of the file's name (filenumber), and I want to loop through the excel files one by one, opening them and extracting the data, then closing them.
There are 500 files, each of the format: img_****ff*******.xlsx, where the first set of asterisks is my filenumber, while the second set of asterisks is unknown.
So far, I have tried listing what is in the directory using:
list=dir('E:\processed\Img*');
filenames={list.name}
This provides with with the full file names.
I tried then within a loop to create the part of the filename I know exists:
x = sprintf('Img_%d_FF_',img(1,1));
I then thought I could use 'Find' to look for my my partial filename/string in the 'filenames' structure above. I don't think I have the code correct for this datatype though:
index = find(strcmp({list.name}, x)==1)
You're pretty close, but the issue is that strcmp compares the whole string and since you only have the beginning part, it is not going to match. I would use strncmp to compare only the first n characters of the string. We can determine what n is based upon the length of your string x.
matches = strncmp({list.name}, x, numel(x));
thisfile = list(matches).name;
I'm having trouble with loading .txt file in Matlab. The main problem is having not equal rows. I'll attach the file so you can more clearly see what I'm truing to say. First, the file has information about each node in graph. One row has information like this:
1|1|EL_1_BaDfG|4,41|5,1|6,99|8,76|9,27|13,88|14,19|15,91|19,4|21,48...
it means:
id|type|name|connected_to, weight|connected_to, weight| and so on..
I was trying to use fscanf function, but it only reads whole line as one string. How I suppose to divide it into struct with information that I need?
Best regards,
Dejan
Here, you can see file that I'm trying to load
An alternative to Stewie answer is to use:
fgetl to read each line
Then use
strread (or textscan) to split the string
Firstly using the | delimiter - then on the sub section(s) containing , do it a second time.
I came across the following lines in MATLAB:
m = dir(fullfile(dataset,'*.png'));
m = {m(~[m.isdir]).name};
I understand that the first line is trying to obtain the .png files from a directory. But, what is the second line trying to perform? isdir seems to determine that an input is a directory. That's what I new for that part. But, what is the line trying to perform?
Thanks.
The second line is getting all files that are not a directory and then getting the respective names and storing them into a cell array
m.isdir indicates if it is a folder or not
returns 1 if it is, 0 if not.
~[m.isdir] will indicate which of the values returned from isdir was a 0.
m(~[m.isdir]) grabs all objects in m determined by the logical indexing done above
m(~[m.isdir]).name gets the names of all of them
{m(~[m.isdir]).name} stores them all in cell array
Hopefully this step by step walkthrough helps.
While I am not sure why the second line is necessary because the fullfile(dataset,'*.png') should only return paths that end in .png, which will not be a folder, I guess it is good to check.
I have several .csv files with similar filenames except a numeric month (i.e. 03_data.csv, 04_data.csv, 05_data.csv, etc.) that I'd like to read into R.
I have two questions:
Is there a function in R similar to
MATLAB's varname and assignin that
will let me create/declare a variable name
within a function or loop that will allow me to
read the respective .csv file - i.e.
03_data.csv into 03_data data.frame,
etc.? I want to write a quick loop to
do this because the filenames are
similar.
As an alternative, is it better to
create one dataframe with the first
file and then append the rest using a
for loop? How would I do that?
You could look at this related question. You can create the file names easily with a paste command:
file.names <- paste(sprintf("%02d",1:10), "_data.csv", sep="")
Once you have your file names (whether by creating them or by reading them from the directory as in the other question), you can import them quickly with an lapply:
import.list <- lapply(file.names, read.csv)
Lastly, to combine the list into one dataframe, the easiest approach is to use the reshape function below:
library(reshape)
data <- merge_recurse(import.list)
It is also very easy to read the content of a directory including use of regular expressions to skip focus on certain names only, e.g.
filestoread <- list.files(someDir, pattern="\\.csv$", full.names=TRUE)
returns all (fully-formed, including full path) files in the given directory someDir that end on ".csv". You can get fancier with better regular expressions which are documented in many places.
Once you have your list of files, it is straightforward to read them all using apply or lapply or a loop.