How to request+input variable name+value then write to file?

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sono 2012-9-13

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采纳的回答： Walter Roberson

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I am trying to write a script that:

asks user for matrix name %like mat1

asks user for matrix value %like [20,30]

writes the matrix to a file

every time the script is run I want new data added to file, NOT overwriting what's already there.

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I use code like this to ask for variable value but don't know how to ask for variable name.

mat1 = input('Enter Name: \n','s');

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I use code like this to write to file but I don't know how to write a variable whose name I do not know prior to user putting it in. I also don't know how to make it so it doesn't over write information already present in file.

fid = fopen('locations.dat', 'w');
fprintf(fid,'%s\n',loc1M);
fclose(fid);

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Answer 1

Walter Roberson 2012-9-13

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To append: Open the file with 'a' instead of 'w'.

You do not need to write a matrix whose name you do not know. In your problem description, the matrix name can be treated as a pure string to be written at output time: you never need to store anything into a variable with that name. Something like

fprintf(fid, '%s\n', matrix_name);
fprintf(fid, '%f ', matrix_value);

except that you need to adjust the writing of matrix value to get the correct number of columns across.

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sono 2012-9-13

编辑：sono 2012-9-13

Thanks for the append tip.

However I do no need to write a matrix who's name and value I do not know (unless I misunderstood something).

This is a script for a user who will not program; ie will not use any functions of any kind.

-User runs the script

-Gets a prompt for location name

-Inputs location name

-Gets prompt for latitude and longitude

-Inputs latitude and longitude

-Script writes the matrix name and values now stored in temp memory to locations.dat file thus building a database.

I do not know what location the user will choose on the surface of the planet nor what the user chooses to name it so I need the script to prompt for all that information and then once it has it write it to file.

Ideally I would have a 1x3 matrix and have [name,lat,long] however apparently you cant have a string and a numeric variable in the same matrix.

After I figure this out the next problem will be a function to scan the file for one of the names it holds and recall the latitude and longitude values to perform calculations using them. Not sure yet how I will accomplish that either.

I figured out how to do this by creating a new file for each location but I want to accomplish this using one file as a database :(

Walter Roberson 2012-9-13

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fprintf(fid, '%s %f %f\n', location_name, latitude, longitude);

sono 2012-9-18

编辑：sono 2012-9-18

THANKS! That seems to work great except it writes

|.wSANJOSE 20.000000 30.000000

plus a little arrow character between "." and "w" that I cant paste in to this window. Any way to get rid of that "|.w" gibberish?

Could you recommend a command to search the file for name and import the adjacent variables (latitude/longitude)?

thanks!

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How to request+input variable name+value then write to file?

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