How to round float numbers in text in C? - c

Question

So I have this text
today average human lifespan in Western countries is approaching and exceeding 80 years.
1 Japan 82.6 123 19
2 Hong Kong 82.2 234 411
3 Iceland 81.8 345 26
4 Switzerland 81.7 456 7
5 Australia 81.2 567 500
...
80 Lithuania 73.0 800 2
...
194 Swaziland 39.6 142 212
195 133714 18.0 133 998
196 100110011 10.0 667 87351
I need to round the float numbers in this text to whole numbers. I've searched a lot of forums but I cannot seem to find what I need.
This text is given in a .txt file. My task: "Round real number(that have decimals) to whole numbers. The corrected text should be in a new .txt" That's it.

Answer 1

scanf and sscanf are your best friend to extract anything of a string.
floor is use full to suppress decimal on a float. Then can be used to round it (to use it include math.h)...
The format string describes the expected format.The function return the number of parameters found.
Sample:
Initialization
int id = -1;
char country[160]; /* /!\ Warning country name length shall be fewer than 160 */
/* Scanf don't care of this array parameter length. If it is too short */
/* It will erase following memory... */
/* That is why scanf are often disparaging */
float percent = 0.0;
char a_number_as_string[10];
int other_number = -1;
char* Switzerland = "4 Switzerland 81.7654321 456 7";
effectif code
int ret = sscanf(Switzerland, "%d %s %f %s %d", &id, country,
&percent, a_number_as_string, &other_number);
if(ret == 5) {
printf("~~ id: %d\n\tcountry: %s\n\tpercent: %.2f\n\tand : "
"(%s, %d)\n", id, country, percent, a_number_as_string,
other_number);
/////// ROUND
printf("*** round");
printf("\twith printf %%.1f = %.1f\n", percent);
printf("\twith printf %%.2f = %.2f\n", percent);
printf("\twith printf %%.3f = %.3f\n", percent);
printf("\twith printf %%.4f = %.4f\n", percent);
printf("*** With floor (included in math.h)\n");
printf("\t1 decimal: %f\n", floor(percent*10)/10);
printf("\t2 decimal: %f\n", floor(percent*100)/100);
printf("\t3 decimal: %f\n", floor(percent*1000)/1000);
printf("\t4 decimal: %f\n", floor(percent*10000)/10000);
} else {
printf("--> ret = %d", ret);
}
output
~~ id: 4
country: Switzerland
percent: 81.70
and : (456, 7)
*** round
with printf %.1f = 81.8
with printf %.2f = 81.77
with printf %.3f = 81.765
with printf %.4f = 81.7654
*** With floor (included in math.h)
1 decimal: 81.700000
2 decimal: 81.760000
3 decimal: 81.765000
4 decimal: 81.765400
This function are describe in Unix, OSX, Unix terminal man pages:
man scanf
man sscanf
man floor
Or you can find it on several copies of this manages on the web for example
scanf
sscanf
floor

Answer 2

here is the program I have already tested it for a single line of input string:-
// LINK - http://stackoverflow.com/questions/40317323/how-to-extract-float-numbers-from-text-in-c#40317323
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
int main()
{
char s[100];
int i,j;
double sum=0.0,frac=0.0;
gets(s); // delimited by '\n' and not by ' '
for( i=0;s[i]!='\0';i++) // for finding index value of decimal point(.)
{
if(s[i]=='.')
break;
}
for(;s[i]!=' ';i--); // for changing key index value to the index value of the first space character(' ') before the decimal point(.)
i++;
for(i;s[i]!='.';i++)
{
sum=sum*10+(s[i]-48); // For extracting integer part
}
i++;
for(i,j=1;s[i]!=' ';i++,j++)
{
frac=frac+(s[i]-48)/pow(10,j); // For extracting fractional part
}
printf("\n\n%lf",sum+frac); // final answer integer part+decimal part
return 0;
}
Explanation:-
okay so what I did is:-
Since scanf() is automatically delimited by space I used gets() which is delimited by new line;
Then we know that there will be a decimal point(.) for floating number in the string, so we find the index value(say key) of the decimal point in the array.
Once we have found the decimal point we know there will only be numbers between the decimal point and the space character after the country name so now we find the index value of that space(key).
Now from that key value we again first move to the decimal point(.) character index while calculating the integer part.Calculated using ASCII value i.e. ASCII value of character Zero(0) is 48 and character Nine(9) is 57 hence subtracting 48 from every character and extracting the value.
Again from the Decimal point(.) to the next space character in the string is part of the floating number and after decimal the numbers follow the weight 10^(-1),10^(-2),10^(-3)...and so on hence the temporary variable and the power() function.Thus we, successfully calculated the fractional part also.
Finally, I just added the Integer and the fractional parts within the printf().
Try, using printf() with all the variables in each of the for loops for better understanding, kinda like dry-run.

Answer 3

You can parse all the values from the string using regex in c#
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Data;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
string[] input = {
"today average human lifespan in Western countries is approaching and exceeding 80 years.",
"1 Japan 82.6 123 19",
"2 Hong Kong 82.2 234 411",
"3 Iceland 81.8 345 26",
"4 Switzerland 81.7 456 7",
"5 Australia 81.2 567 500",
"80 Lithuania 73.0 800 2",
"194 Swaziland 39.6 142 212",
"195 133714 18.0 133 998",
"196 100110011 10.0 667 87351"
};
string pattern = #"(?'index'\d+)\s+(?'country'.*)\s+(?'float'[^ ]+)\s+(?'num1'\d+)\s+(?'num2'\d+)$";
for (int i = 1; i < input.Length; i++)
{
Match match = Regex.Match(input[i], pattern);
Console.WriteLine("index : '{0}', country : '{1}', float : '{2}', num1 : '{3}', num2 : '{4}'",
match.Groups["index"],
match.Groups["country"],
match.Groups["float"],
match.Groups["num1"],
match.Groups["num2"]
);
}
Console.ReadLine();
}
}
}