Trying to format a scientific number in PHP:
sprintf(%'1.2E',$var)
This gets me to 5.01E+1
I am trying to print 2 digits after the + sign
The parser requires the number format to be:
5.01E+01 instead of 5.01E+1
Is it possible to achieve this format with sprintf?
Is there any other method that can achieve this?
Thanks for looking
I couldn't find a way to do it solely with sprintf but I believe the following would be closer to the "correct" way to do it. The following calculates the exponent from the base-10 logarithm.
You can then pass the original value (dividing by 10 to the power of the exponent) and the exponent to the sprintf function as a float and an integer respectively. You can force the positive + sign remembering that it counts towards the character / padding length.
function scientificNotation($val){
$exp = floor(log($val, 10));
return sprintf('%.2fE%+03d', $val/pow(10,$exp), $exp);
}
demo / test cases :
scientificNotation(5.1); // 5.10E+00
scientificNotation(50.1); // 5.01E+01
scientificNotation(500.1); // 5.00E+02
scientificNotation(0.0051); // 5.10E-03
There is no built-in method as far as I know. But with a little bit of Regex black magic you can do something like this:
preg_replace('/(E[+-])(\d)$/', '${1}0$2', sprintf('%1.2E',$var));
Notice that I just wrapped your call to sprintf() with an appropriate call to preg_replace(). If the regular expression does not match it will leave the output from sprintf() as is.
The above answers both work great.
Also found out I can use:
$var_formatted = shell_exec("printf '%1.2E' $var");
which could be the cleanest given the script has the permissions to execute commmands.
The E+nn format is the default output format for the linux shell printf.
From the shell:
:~$ echo `printf '%1.2E' 500`
5.00E+02
:~$ echo `printf '%1.2E' 5`
5.00E+00
:~$ echo `printf '%1.2E' 0.05`
5.00E-02
Related
I want to show a float number in php string.
something like:
My float number is: 0.00003485
But when I am using echo I see it like this:
My float number is: 3.485E-5
Also, I know I can use printf("%.10f",$float) code, but I need to use it in lots of places in my string, So I can't use printf.
What code should I use on a string, to show floats as they are? I don't want that shorted number (3.485E-5).
At some condition i am prefer declaration float number as string:
MyFloatNumber = "0.0000000000000000000000003485";
so,
echo MyFlatNumber;
//0.0000000000000000000000003485
I know I can use printf("%.10f",$float) code, but I need to use it in lots of places in my string, So I can't use printf.
I have to respectfully disagree with that:
printf('My float number is: %1$.8f (again: %1$.8f; once more: %1$.8f)', 0.00003485);
Or, if you need it in a string:
$foo = sprintf('My float number is: %1$.8f (again: %1$.8f; once more: %1$.8f)', 0.00003485);
Of course, if you mean it's against project style guidelines or company policy, that's another story.
What code should I use on a string, to show floats as they are?
Really? Floats in PHP are a 64-bit IEEE 754 double precision format bitmap. According to this online converter, number 0.00003485 would be:
0010010001010111110011100001110100101110111001001111
Of course, they aren't actual ones and zeroes but different voltage levels ;-)
You can write a function to handle this in any way you want. Why not?
function fval($f, $precision = 9) {
return number_format($f, $precision);
}
Then any place you need to format, call it out:
$f = 3.485E-5;
echo fval($f); // this will print: 0.000003485
In PHP I have the following code:
<?PHP
$var = .000021;
echo $var;
?>
the output is 2.1E-5 !
Why? it should print .000021
Use number_format() to get what you're after:
print number_format($var, 5);
Also check sprintf()
2.1E-5 is the same number as 0.000021. That's how it prints numbers below 0.001. Use printf() if you want it in a particular format.
Edit If you're not familiar with the 2.1E-5 syntax, you should know it is shorthand for 2.1×10-5. It is how most programming languages represent numbers in scientific notation.
Use number_format or sprintf if you want to see the number as you expect.
echo sprintf('%f', $var);
echo number_format($var, 6);
To show a number up to 8 decimal spaces, without extra zeroes to the right (as number_format does, which can be annoying), use this:
echo rtrim(rtrim(sprintf('%.8F', $var), '0'), ".");
In general, a number is a number, not a string, and this means that any programming language treats a number as a number. Thus, the number by itself doesn't imply any specific format (like using .000021 instead of 2.1e-5). This is nothing different to displaying a number with leading zeros (like 0.000021) or aligning lists of numbers. This is a general issue you'll find in any programming language: if you want a specific format you need to specify it, using the format functions of your programming language.
Unless you specify the number as string and convert it to a real number when needed, of course. Some languages can do this implicitly.
The previous answers responded to OP question, but none offered the code to do it.
Use this function to format any number with E- format.
function format_amount_with_no_e($amount) {
$amount = (string)$amount; // cast the number in string
$pos = stripos($amount, 'E-'); // get the E- position
$there_is_e = $pos !== false; // E- is found
if ($there_is_e) {
$decimals = intval(substr($amount, $pos + 2, strlen($amount))); // extract the decimals
$amount = number_format($amount, $decimals, '.', ','); // format the number without E-
}
return $amount;
}
Please note the function will always return a string.
Programming languages have different methods for storing numbers in memory. This is determined by the type of number that is being used. In your case, you have a floating point number (a fraction) that is to large to be stored as a fixed point number ( fractions are stored in this manner depending on their size).
This is a very important feature especially when working with very large or very small numbers. For instance, NASA or spaceX uses special storage methods for its calculations to ensure that the rockets the re-enter earths orbit land where they should.
Also, different storage methods take up different amounts of memory. However, the solution provided above should work. Just remember round off errors might occur with very big or small numbers.
So I got a really long string, made by a calculator.
$string='483451102828322427131269442894636268716773727170';
$result=(8902543901+$string)*($string/93.189)/($string)+55643907015.57895461;
echo $result;
This outputs 5.1878558931668E+45
So now my question is. How can I output the whole string, without that nasty E+45?
PHP on a 64 bit machine can only accurately calculate number up until 9223372036854775807. As soon as you calculate with numbers higher than that, php will switch to floats which may loose some of it's precision, especially when you use divisions.
There's an extension for php that will allow you to make calculations based on string, called BCMath.
Example:
$string = '483451102828322427131269442894636268716773727170';
$result = bcadd($string, 8902543901);
echo $result;
bcadd() is for additions, bcdiv() for divisions and bcmul() for multiplying.
You can't print exact value because you are using calculation, so this $string becomes a number (float in this case) and all numbers have limited precision.
If you want to do operations on big numbers you should use BCMath
However if you want to display it without scientific notation you can do it using:
echo sprintf("%f",$result);
or
echo sprintf("%.0f",$result);
if you want to omit decimal part
I have the following line of code in javascript:
(Math.random() + "") * 1000000000000000000
which generates numbers like:
350303159372528000
I tried the same thing in PHP with this:
rand()*1000000000000000000
Which returns:
2.272e+21
I need to use PHP as the number generated will be stored as a SESSION variable and will be used by JavaScript later on.
How do I get PHP to force the number to be an int rather than a float?
EDIT PHP seems to struggle with this.
Would it work if I just generated the rand number in PHP saved it to the SESSION and then done the multiplying by 1000000000000000000 in JavaScript?
How would I go about this?
I'd recommend calling
PHP_INT_MAX
To see if your PHP installation can handle an integar that large. I'm guessing it can't which is why it is knocking it down to scientific notation.
I'd suggest converting your result to an int:
intval(rand()*1000000000000000000)
That said, see Kolink and Jeremy1026 answers for precision issues. If you only need an unique identifier, see Truth's answer.
Update: if you're using strings to represent your numbers, don't want or can't use an arbitrary precision library, and don't stricly need perfecly fair random numbers, you could generate smaller numbers and concat them together:
strval(rand()*999999999 + 1) . strval(rand()*1000000000)
(The +1 is to avoid a leading zero in your result; note also that your number will never have a single digit, but every other number is possible)
For a random number with (exactly) 18 digits, you can also use str_pad in the 2nd part, to fill it with leading zeros:
strval(rand(100000000,999999999)) .
str_pad(strval(rand(0,999999999)), 9, "0", STR_PAD_LEFT)
If you need a unique identifier (which is what it looks like you're trying to do), please use PHP's uniqid() function.
floor() / ceil() / round() / (int) / intval() will convert the number to int.
Also, rand() takes two arguments. If ints are supplied - it will return an integer
And printf() should take care of printing in the format you wish (printf('%d', $int) should do the trick)
In the end I solved the issue like this:
<?php
error_reporting(0);
function RandNumber($e){
for($i=0;$i<$e;$i++){
$rand = $rand . rand(0, 9);
}
return $rand;
}
echo RandNumber(18);
// Outputs a 18 digit random number
?>
In PHP I have the following code:
<?PHP
$var = .000021;
echo $var;
?>
the output is 2.1E-5 !
Why? it should print .000021
Use number_format() to get what you're after:
print number_format($var, 5);
Also check sprintf()
2.1E-5 is the same number as 0.000021. That's how it prints numbers below 0.001. Use printf() if you want it in a particular format.
Edit If you're not familiar with the 2.1E-5 syntax, you should know it is shorthand for 2.1×10-5. It is how most programming languages represent numbers in scientific notation.
Use number_format or sprintf if you want to see the number as you expect.
echo sprintf('%f', $var);
echo number_format($var, 6);
To show a number up to 8 decimal spaces, without extra zeroes to the right (as number_format does, which can be annoying), use this:
echo rtrim(rtrim(sprintf('%.8F', $var), '0'), ".");
In general, a number is a number, not a string, and this means that any programming language treats a number as a number. Thus, the number by itself doesn't imply any specific format (like using .000021 instead of 2.1e-5). This is nothing different to displaying a number with leading zeros (like 0.000021) or aligning lists of numbers. This is a general issue you'll find in any programming language: if you want a specific format you need to specify it, using the format functions of your programming language.
Unless you specify the number as string and convert it to a real number when needed, of course. Some languages can do this implicitly.
The previous answers responded to OP question, but none offered the code to do it.
Use this function to format any number with E- format.
function format_amount_with_no_e($amount) {
$amount = (string)$amount; // cast the number in string
$pos = stripos($amount, 'E-'); // get the E- position
$there_is_e = $pos !== false; // E- is found
if ($there_is_e) {
$decimals = intval(substr($amount, $pos + 2, strlen($amount))); // extract the decimals
$amount = number_format($amount, $decimals, '.', ','); // format the number without E-
}
return $amount;
}
Please note the function will always return a string.
Programming languages have different methods for storing numbers in memory. This is determined by the type of number that is being used. In your case, you have a floating point number (a fraction) that is to large to be stored as a fixed point number ( fractions are stored in this manner depending on their size).
This is a very important feature especially when working with very large or very small numbers. For instance, NASA or spaceX uses special storage methods for its calculations to ensure that the rockets the re-enter earths orbit land where they should.
Also, different storage methods take up different amounts of memory. However, the solution provided above should work. Just remember round off errors might occur with very big or small numbers.