How to overwrite a file in matlab

Matlab specifically mentions that Matlab overwrites an existing variable when using -append.

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To read a file "Daughters. However, there are other, easier-to-use functions available that perform the same tasks with a performance penalty. Next, load in the existing file to get all of the variables in the file. Thanks, Wes If you would like to refer to this comment somewhere else in this project, copy and paste the following link: Roger Dugan - We need to understand this problem so we can address it. This is annoying, and possibly not worth fixing I don't see how else you can update variables in a file. If you have an all-numeric matrix, the dlmread and dlmwrite functions work just as well unless a certain numeric precision is required for input or output. In that case, I would recommend looking into the Matlab documentation on how to close all open file handles. However, if I run the exact same program with or without changes , the overload file does not get overwritten. By default if you don't specify a permission , you only have read permission when you open a file. Consult the fprintf documentation for details on the supported specifiers. This leads me to believe that it is Matlab which has the issue. If that solves the problem, then it appears from my limited knowledge that the COM client wasn't letting go of the file handles. The alternative, which Matlab seems to do, is to open the file for reading, parse through all contents, and copy all the unduplicated variables to a new file, save in the new or duplicated appended variables, close the file, and then rename the new temporary file to the old one. I would say it is well worth fixing.

Use evalin or somesuch to import the variables that are to be appended. This only works reliably for numeric matrices.

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Thanks, If you would like to refer to this comment somewhere else in this project, copy and paste the following link: wsunderm1 - It appears as though either the COM object or Matlab still has a handle open to that file.

The alternative, which Matlab seems to do, is to open the file for reading, parse through all contents, and copy all the unduplicated variables to a new file, save in the new or duplicated appended variables, close the file, and then rename the new temporary file to the old one.

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I'm pretty sure Octave just relies on opening the file in 'append' mode and adding the data at the end of the file. This creates an overload report. But, if you have 2GB arrays, then this is going to be cumbersome. Finally, write out all variables in the temporary namespace to the file. This leads me to believe that it is Matlab which has the issue. Reading such files can also be done using the textscan function, as long as the format of all of the lines is consistent i. Just wanted to double-check this possibility. If you have an all-numeric matrix, the dlmread and dlmwrite functions work just as well unless a certain numeric precision is required for input or output. To other users, they are useful if more control is needed over how files are read or if the built-in and MATLAB contributor central functions fail to read the file. It might be hard to do though But the overload report isn't even open! And I would also say that efficiency is a big deal. I would say it is well worth fixing. Anonymous Quote Mike is correct.

If efficiency isn't a big deal, it might be possible to work at the m-file level in a separate namespace. Just to make sure, are you opening the overload report inside of Matlab and parsing it, but leaving the file open outside of the solve loop?

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Opening and closing files[ edit ] In order to use the low-level functions to read and write to a file, you have to open the file first. Low-level functions[ edit ] If you are familiar with reading and writing files in C, these functions will seem familiar. Next, load in the existing file to get all of the variables in the file. If that solves the problem, then it appears from my limited knowledge that the COM client wasn't letting go of the file handles. This is annoying, and possibly not worth fixing. Just wanted to double-check this possibility. This only works reliably for numeric matrices. However, there are other, easier-to-use functions available that perform the same tasks with a performance penalty. This creates an overload report. Anonymous Quote Mike is correct. This leads me to believe that it is Matlab which has the issue. In that case, I would recommend looking into the Matlab documentation on how to close all open file handles. Reading such files can also be done using the textscan function, as long as the format of all of the lines is consistent i. Consult the fprintf documentation for details on the supported specifiers. Vectorization of printing and scanning functions[ edit ] Unlike the C version of fscanf and fprintf, the printing and scanning functions of MATLAB are "vectorized", which means you can pass a matrix to fprintf and have it print all of the lines for you with the same formatting, or you can ask fscanf to read each line of the file the same way and return a matrix to you.

Reading such files can also be done using the textscan function, as long as the format of all of the lines is consistent i. But, if you have 2GB arrays, then this is going to be cumbersome.

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