Grouping imported data and exporting into a .txt file

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Jia Qing Soo 2013-10-3

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https://ww2.mathworks.cn/matlabcentral/answers/89086-grouping-imported-data-and-exporting-into-a-txt-file

评论： Cedric 2013-10-3

I am suppose to import the following data from a .txt and then sort them accordingly. Those in bold are the variables, depending on the imported data. The sorting is done (>=80) - distinction, (>=50, <=79) - pass, (<=49) - file.

*56

88

32

16

99

78

44

63*

-----------------------------------------------------------------

The sample output to a .txt file is,

2 students scored a distinction. Their scores are

*88

99*

3 students scored a pass. Their scores are

*56

78

63*

3 students scored a fail. Their scores are

*32

16

44*

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Cedric 2013-10-3

And what have you done or tried by yourself so far?

Jia Qing Soo 2013-10-3

Thus far i have,

clear;clc;

fid = fopen('Input.txt');

a = fscanf(fid,'%g',inf);

fclose(fid);

len = length(a);

fid2 = fopen('Output.txt','wt');

I was thinking of using "if,else" but have no idea how to continue the code.

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Answer 1

Cedric 2013-10-3

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编辑：Cedric 2013-10-3

在 MATLAB Online 中打开

Ok, the code that you provided in your comment is a good start. Here is a hint: define

>> x = [9, 3, 6, 7, 1, 2] ;

Then, for example

 >> cond = x > 5
 cond =
     1     0     1     1     0     0

is a vector of logicals whose elements indicate where the condition is true (1) or false (0) for each element of x. A remarkable property of these vectors of logicals is that you can use them for indexing the original vector x, i.e. for getting all elements which satisfy the condition:

 >> y = x(cond)
 y =
     9     6     7

Now you can work with y, e.g. compute its length, output it to file, etc..

Once you'll understand that, you'll have all you need to go on with this homework I guess.

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Jia Qing Soo 2013-10-3

编辑：Jia Qing Soo 2013-10-3

However, i am still having problem with the fprintf portion.

cond = a>= 80

y = a(cond)

fprintf('%g students scored a distinction. Their scores are\n%g',___,y)

The "___" is the portion i have no idea what to type. How do i calculate the length of variables that has >= 80? And my "y" has 2 numbers, so how do i display both numbers?

Expected output is,

2 students scored a distinction. Their scores are

*88

99*

Cedric 2013-10-3

在 MATLAB Online 中打开

For the first question:

doc length

For the second question, you cannot output an array with only one %g at the end of this formatSpec string that you are using. You have essentially two options: the first is a FOR loop over elements of vector y, which prints '%g\n' for each element. The second is a print using the same format '%g\n' directly on the y array, and use the fact that FPRINTF repeats the format as long as it "finds elements to output in the array".

I cannot say much more without giving you the answer directly. The best thing that you can do is to experiment with a small y array that you build by hand, and see whether you can understand what I said about repeated format, or try to implement a FOR loop.

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