fprintf problem, can't print

My code is as follow:

for i = 1:length(Ta)
    fprintf(fid, '%s;%.2f;%.2f;%.2f;%.2f\n', DateTimeStr(i), Ta(i), Pa(i), Tb(i), Pb(i));
end

DateTimeStr(i) is an string array of 14 characters. Ta(i), Pa(i), Tb(i), Pb(i)) are floating number.

Somehow in my text file DateTimeStr(i) only print 1 character, the rest is OK. Here is how it print to file:

2;55.05;87.82;54.26;84.27
2;55.04;87.80;54.26;84.27
2;55.07;87.81;54.26;84.28
2;55.04;87.81;54.25;84.28
2;55.03;87.81;54.25;84.28

it should be like this

20120906093000;55.04;87.80;54.26;84.27
20120906093100;55.07;87.81;54.26;84.28
20120906093200;55.04;87.81;54.25;84.28
20120906093300;55.03;87.81;54.25;84.28

[Jan]

What exactly is "a string array of 14 characters"? Obviously "DateTimeStr(i)" causes the problem, so please post exactly the type and size of this variable as well as its contents.

In my test it works as expected:

D = ["12345678901234", "12345678901234"]
fprintf('%s;\n' D(1));

So please explain the difference of this simple example and your data.

Answer 1

[Star Strider]

Since ‘DateTimeStr’ is likely an character array, you have to address it as such in the variable reference to it:

fprintf(fid, '%s;%.2f;%.2f;%.2f;%.2f\n', DateTimeStr(i,:), Ta(i), Pa(i), Tb(i), Pb(i));

[Jan]

+1. Good guess.

[Stephen23]

Then why is it always displaying as 2, although the loop index is increasing?

[Star Strider]

@Jan — Thank you!

@Stephen — The reference to ‘DateTimeStr(i)’ defaults to ‘DateTimeStr(i,1)’, so only the first ‘2’ prints.

Testing that with:

DateTimeStr = ['20120906093000'
               '20120906093100'
               '20120906093200'
               '20120906093300'];
A = [55.04,87.80,54.26,84.27
55.07,87.81,54.26,84.28
55.04,87.81,54.25,84.28
55.03,87.81,54.25,84.28];
Ta = A(:,1);
Pa = A(:,2);
Tb = A(:,3);
Pb = A(:,4);

fid = 1;
for i = 1:length(Ta)
    fprintf(fid, '%s;%.2f;%.2f;%.2f;%.2f\n', DateTimeStr(i,:), Ta(i), Pa(i), Tb(i), Pb(i));
end

produces:

20120906093000;55.04;87.80;54.26;84.27
20120906093100;55.07;87.81;54.26;84.28
20120906093200;55.04;87.81;54.25;84.28
20120906093300;55.03;87.81;54.25;84.28

as desired.

I suspect Jan’s test worked because he used string variables, and my code assumes a character array.

[Stephen23]

@Star Strider: that makes sense. I was mislead by the description "a string array of 14 characters", and somehow thought this was a vector. Oh well.

[Star Strider]

It confused me too at first.

I experimented by printing it first with a single subscript, (printing only a 2), then adding the second subscript and printing the entire character vector. That’s when I figured out that ‘DateTimeStr’ is an array of character vectors, since only that assumption will produce the observed results.