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Index › Programming Questions & Help › Syntax Questions › min() returns value not in array
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min() returns value not in array (Read 1865 times)
danielle
min() returns value not in array
May 28th, 2010, 3:10am  
Hi all,

I've got an array with 828 items (floats). I want to search for the max and min value. max(array_name) returns 65.8 which is correct. But min(array_name) returns 0.0, a value that isn't in the array. I don't have any empty items either in the array.

Does anybody know what's hapening here and how this can be helped?

Thanks very much in advance, best, danielle
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Cedric
Re: min() returns value not in array
Reply #1 - May 28th, 2010, 3:38am  
hmm as it is working in this example :

float[] numbers = { 9.10, 1.50,23.0, 15.3323,0.355, 3.36, 3.03 };
println(max(numbers));
println(min(numbers));

it should in yours if there is nothing wrong with your array.
Do you have a way to check your array. Where do you get the data from? how do you load it ?
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Smitty
Re: min() returns value not in array
Reply #2 - May 28th, 2010, 5:03am  
Along with Cedric's questions: is 0.0 lower than all the values in your array?  i.e., if 0.0 was in the array, would it be the correct min?
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danielle
Re: min() returns value not in array
Reply #3 - May 28th, 2010, 5:26am  
@Cedric, this works fine, I've also done a test with a simple array.
@Smitty, yes 0.0 would be the lowest value had it been in the array. I test the array by printing all the values with a string in front of it ("val: ") so I can see that all the items are filled. I don't get an empty val: Just val: 51.3 etc.
I load the values from a text file which starts like this:
Tijd|Decibel|Stress
10:25:12|51.6|85
10:25:02|44.1|85
10:24:52|59.7|84
10:24:42|52.6|85
10:24:32|49.8|83
10:24:22|51.2|82
10:24:12|44.8|81
10:24:02|56.1|79
10:23:52|52.1|80
10:22:32|53.5|53
10:23:42|41.8|82
10:23:32|49|84
10:23:22|46|77
10:23:02|52.1|71
10:23:12|50.9|69
10:22:52|49|72
10:22:42|54.9|62
10:25:22|51.1|78
10:25:32|54.7|80
... etc
The summarized code:
Code:

// load data from file
String [] rows = loadStrings(filename);
float [] db_val = new float[rows.length];
// I start the for loop at 1 to skip the text line
  for(int i=1; i<rows.length; i++)
  {
    String tmp_val[] = split(rows[i], "|");
    // get second column
    float d = float(tmp_val[1]);
    // store db values in array
    db_val[i] = d;
    println ("val: "+d);
    float db_max = max(db_val);
    float db_min = min(db_val);
    print("max: ");
    println(db_max); // 65.8
    print("min: ");
    print(db_min); // 0.0
  }

Oh, I just printed db_val[0] and it returns 0.0 ....
Now I try: db_val[i-1] = d; // db_val[0] = 51.6 which is correct but the min() still returns 0.0

Hope you can help, tia.
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Smitty
Re: min() returns value not in array
Reply #4 - May 28th, 2010, 5:48am  
danielle wrote on May 28th, 2010, 5:26am:
Oh, I just printed db_val[0] and it returns 0.0 ....
Now I try: db_val[i-1] = d; // db_val[0] = 51.6 which is correct but the min() still returns 0.0

You've got the right idea.  The code you quoted never sets db_val[0], so it remains 0.0.  But when you change to db_val[i-1] = d; you leave the last element of db_val untouched, so it remains 0.0, which is then the minimum.

The solution is to keep the second version and use:

Code:
float [] db_val = new float[rows.length-1];


which gets you an array of exactly the right length.
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danielle
Re: min() returns value not in array
Reply #5 - May 28th, 2010, 5:56am  
Great, I've got it now, thanks.
I was searching just now for an easy way to print the array content. Like you do in PHP with var_dump or just a trace statement in ActionScript. Is there a method or function in Processing to do this?

Thanks again, d
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PhiLho 
Re: min() returns value not in array
Reply #6 - May 28th, 2010, 6:08am  
Code:
float[] numbers = { 9.10, 1.50,23.0, 15.3323,0.355, 3.36, 3.03 };
println(numbers);

One of the many convenient shortcuts provided by Processing... Smiley
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danielle
Re: min() returns value not in array
Reply #7 - May 28th, 2010, 6:30am  
Smiley
OK, pfff, I did print(array_name) and got gibberish but println gives a nice overview. Thanks.
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