problem in a code with filehandling

[neha_chhatre]

i have a wierd problem...iam not able to understand wat is goin
wrong...i have written a code which reads the values form a text file
(it contains lot of values like time=1.147279,value=240.66 and so
on................)
the code is workin well for the firs five iterations...but thn it isnt
doing the computations properly after the 5th iteration (sumthing is
goin wrong in the if loop)
pls help me out with this
Iam posting the entire code here.......

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
FILE *fp;
char ch,str[100],str1[100];

int c=0,i,j;
float t=0.0,t1=1.0472789115646258,t2=0.0,sum=0.0,avg=0.0,check=0.0;

fp=fopen("pt1.txt","rb");
if (fp==NULL)
perror ("Error opening file: pt1.txt");
else
{
while(!feof(fp))
{

fscanf (fp, "%s", str);
i=strcmp(str,"time");
if(i==0)
{
printf("t1=%f\n",t1);
fscanf (fp, "%s", str);
fscanf (fp, "%f",&t);


fscanf (fp, "%s", str);
j=strcmp(str,"value");


if(j==0)
{
fscanf (fp, "%s", str);
fscanf (fp, "%f",&t2);
printf("t2=%f\n",t2);
}

check=t1+0.1;


printf("t=%f\n",t);
printf("check=%f\n",check);

if(t==check)
{

sum=sum+t2;
c++;
printf("sum=%f\n",sum);
printf("c=%d\n",c);
}

else
{

printf("sum=%f\n",sum);
sum=0.0;
printf("c=%d\n",c);
c=0;
sum=sum+t2;
c++;
}

t1=t;

}
}
fclose(fp);
}

//printf("%d",c);
}

 

[Mark McIntyre]

i have a wierd problem...iam not able to understand wat is goin
wrong...i have written a code which reads the values form a text file
(it contains lot of values like time=1.147279,value=240.66 and so
on................)
the code is workin well for the firs five iterations...but thn it isnt
doing the computations properly after the 5th iteration (sumthing is
goin wrong in the if loop)
pls help me out with this
Iam posting the entire code here.......

You didn't tell us what the file contained, or what the actual error
was. Post an example of the input and output, and where you think its wrong.

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
FILE *fp;
char ch,str[100],str1[100];

int c=0,i,j;
float t=0.0,t1=1.0472789115646258,t2=0.0,sum=0.0,avg=0.0,check=0.0;

Float is often a bad choice for mathematical work. The precision is
quite poor, and large errors can rapidly creep in.

 

[neha_chhatre]

i have a wierd problem...iam not able to understand wat is goin
wrong...i have written a code which reads the values form a text file
(it contains lot of values like time=1.147279,value=240.66 and so
on................)
the code is workin well for the firs five iterations...but thn it isnt
doing the computations properly after the 5th iteration (sumthing is
goin wrong in the if loop)
pls help me out with this
Iam posting the entire code here.......

You didn't tell us what the file contained, or what the actual error
was. Post an example of the input and output, and where you think its wrong.

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
FILE *fp;
char ch,str[100],str1[100];

int c=0,i,j;
float t=0.0,t1=1.0472789115646258,t2=0.0,sum=0.0,avg=0.0,check=0.0;

Float is often a bad choice for mathematical work. The precision is
quite poor, and large errors can rapidly creep in.

--
Mark McIntyre

CLC FAQ <http://c-faq.com/>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt>

the following is the file from which it is
reading...........................

File type = "ooTextFile"
Object class = "PitchTier"

xmin = 0
xmax = 6.394557823129252
points: size = 35
points [1]:
time = 1.1472789115646258
value = 240.66658330751105
points [2]:
time = 1.2472789115646257
value = 216.47978246677724
points [3]:
time = 1.3472789115646258
value = 213.83812093716932
points [4]:
time = 1.5472789115646257
value = 210.37648018254478
points [5]:
time = 1.6472789115646258
value = 208.79273834549744
points [6]:
time = 1.8472789115646258
value = 293.3823227689563
points [7]:
time = 1.9472789115646258
value = 316.2633425010987
points [8]:
time = 2.2472789115646257
value = 308.46478338913266
points [9]:
time = 2.3472789115646258
value = 307.8444703977845
points [10]:
time = 2.547278911564626
value = 338.96553268786244
points [11]:
time = 2.647278911564626
value = 337.6384445324801
points [12]:
time = 2.7472789115646257
value = 320.43356977473394
points [13]:
time = 2.8472789115646258
value = 350.33687575048003
points [14]:
time = 2.947278911564626
value = 339.12697914942277
points [15]:
time = 3.047278911564626
value = 342.5515254707035
points [16]:
time = 3.2472789115646257
value = 290.77981793170835
points [17]:
time = 3.3472789115646258
value = 293.72811030038724
points [18]:
time = 3.447278911564626
value = 303.46745549186284
points [19]:
time = 3.947278911564626
value = 251.79416408537938
points [20]:
time = 4.047278911564626
value = 262.28892941664037
points [21]:
time = 4.147278911564626
value = 263.794192151598
points [22]:
time = 4.347278911564626
value = 265.84866240601593
points [23]:
time = 4.447278911564626
value = 266.4690280226695
points [24]:
time = 4.647278911564626
value = 248.27757140917547
points [25]:
time = 4.747278911564626
value = 247.62318109614935
points [26]:
time = 4.947278911564626
value = 251.98088433688451
points [27]:
time = 5.047278911564626
value = 247.5383244834772
points [28]:
time = 5.147278911564626
value = 250.96662855461412
points [29]:
time = 5.347278911564626
value = 223.52314951535087
points [30]:
time = 5.447278911564626
value = 217.52840276529471
points [31]:
time = 5.647278911564626
value = 218.32213379066525
points [32]:
time = 5.747278911564626
value = 219.62413166853094
points [33]:
time = 5.947278911564626
value = 195.49632735594062
points [34]:
time = 6.047278911564626
value = 198.72166439274508
points [35]:
time = 6.147278911564626
value = 202.25686901387476

 

[Bartc]

What exactly is it doing wrong? What should the output be at the sixth
iteration (at points[6] in the file?).

 

[Mark McIntyre]

You didn't tell us what the file contained, or what the actual error
was. Post an example of the input and output, and where you think its wrong.

the following is the file from which it is
reading...........................

File type = "ooTextFile"
Object class = "PitchTier"

xmin = 0
xmax = 6.394557823129252
points: size = 35
points [1]:
time = 1.1472789115646258
value = 240.66658330751105

You can't store these entire values in a float which has precision
typically of around 6 sig figs. You can't store them in a double either,
but the error will be smaller. In both cases, the actual value stored
will be truncated, and when you do maths with it, the discrepancy will
scale up accordingly.

Also you still didn't tell us the error, or why you think its wrong.

 

[Ben Bacarisse]

the code is workin well for the firs five iterations...but thn it isnt
doing the computations properly after the 5th iteration (sumthing is
goin wrong in the if loop)

On my system it works with the data you posted elsewhere (as far as I
can tell). What is it that goes wrong?

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
FILE *fp;
char ch,str[100],str1[100];

int c=0,i,j;
float t=0.0,t1=1.0472789115646258,t2=0.0,sum=0.0,avg=0.0,check=0.0;

fp=fopen("pt1.txt","rb");
if (fp==NULL)
perror ("Error opening file: pt1.txt");
else
{
while(!feof(fp))

Not usual the wight way to do input in C. See the FAQ at
http://c-faq.com/ (specifically Q 12.2).

{

fscanf (fp, "%s", str);
i=strcmp(str,"time");
if(i==0)
{
printf("t1=%f\n",t1);
fscanf (fp, "%s", str);
fscanf (fp, "%f",&t);


fscanf (fp, "%s", str);
j=strcmp(str,"value");


if(j==0)
{
fscanf (fp, "%s", str);
fscanf (fp, "%f",&t2);
printf("t2=%f\n",t2);
}

check=t1+0.1;

This is very convoluted. fscanf can tell you if the input looks right
(i.e. has the right fixed strings in it) and can tell you that the
numbers were read and converted correctly. For example:

do {
switch (fscanf(fp, "time = %f value = %f", &t, &v)) {
case 2:
printf("%f %f\n", t, v); /* change this to do what you want */
break;
case 1:
printf("Time not followed by value.\n");
break;
default:
fgetc(fp);
}
} while (!feof(fp));

It relies on allowing fscanf to fail a lot, but unless you need
blistering speed, that won't be a problem.

 

[Herbert Rosenau]

i have a wierd problem...iam not able to understand wat is goin
wrong...i have written a code which reads the values form a text file
(it contains lot of values like time=1.147279,value=240.66 and so
on................)
the code is workin well for the firs five iterations...but thn it isnt
doing the computations properly after the 5th iteration (sumthing is
goin wrong in the if loop)
pls help me out with this
Iam posting the entire code here.......

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
FILE *fp;
char ch,str[100],str1[100];

int c=0,i,j;
float t=0.0,t1=1.0472789115646258,t2=0.0,sum=0.0,avg=0.0,check=0.0;

fp=fopen("pt1.txt","rb");
if (fp==NULL)
perror ("Error opening file: pt1.txt");
else
{
while(!feof(fp))

As you have'nt tried to read a single byte from the file the while
will loop on

{

fscanf (fp, "%s", str);

As you does NOT test the result of fscanf() you continues into
unspecified behavior when it ends with either EOF oer error, so str
may not changed as you expected

i=strcmp(str,"time");
if(i==0)
{
printf("t1=%f\n",t1);
fscanf (fp, "%s", str);
fscanf (fp, "%f",&t);


fscanf (fp, "%s", str);

Same as above; no test for EOF or error is done, so any error or EOF
left undedected.

j=strcmp(str,"value");


if(j==0)
{
fscanf (fp, "%s", str);
fscanf (fp, "%f",&t2);

same as above

printf("t2=%f\n",t2);
}

check=t1+0.1;


printf("t=%f\n",t);
printf("check=%f\n",check);

if(t==check)
{

sum=sum+t2;
c++;
printf("sum=%f\n",sum);
printf("c=%d\n",c);
}

else
{

printf("sum=%f\n",sum);
sum=0.0;
printf("c=%d\n",c);
c=0;
sum=sum+t2;
c++;
}

t1=t;

}
}
fclose(fp);
}

//printf("%d",c);
}

Nobody can tell what wents wrong because you have too many (excactly
more than 0) attempts to read without a test for success.

--
Tschau/Bye
Herbert

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