Filling a string with characters '#' and space to create bar-graph

[nigelmercier]

I want to create a bar-graph display using a string. The string needs to be 14 characters long, filled from the left with either a '#' character or a ' ' depending on the value of a variable, level.

Each character represents 1/14 of the total (this is my display width), so as level rises from 0 to 14, there will be more # characters on the left, and fewer spaces, viz:

If level < 1, the string should be:  "              "
If level == 1, the string should be: "#             "
If level == 7, the string should be: "#######       "
If level == 14, the string should be: "##############"

I started by using a for loop, but it looked very messy. Is there a shortcut in ANSI C?

Note: I'm a newbie, so would appreciate simple suggestions, without pointers if possible!

[nigelmercier]

BTW, in case anyone thinks to suggest a neater display method using points and lines, or other graphics.

This is for use on a microcontroller and must be done like this. I also lied about using a #. I just can't create the actual character here as it is a self created character (to replace the Yen character in the ASCII set), and it looks like the bars in a bar-graph :)

[jkmyoung]

One possible way is to have a hardcoded string, and use memcpy from string.h in the standard library.

fullStr: "##############"
if (level > 0)
memcpy(str, fullStr, level);

Might be easier if you post your for loop code, and we edited that.

[donbock]

Another way would be to have an array of all 15 possible bar graph strings and compute an array index based on your level variable.

[nigelmercier]

@jkmyoung
In fact my loop code does not work, but here it is:

 void upDisp(void)
{ // Update display
  char bargraph[15] = "0123456789ABCD";
  byte level;
 
  fuelRead8 = getFuel();       // get ADC value from channel 0
  ByteToStr(fuelRead8, txt4);  // convert to string for display
  strLCD11XY(txt4, 0, 0);      // display on LCD in large font at 0,0
 
  level = (fuelRead8/18); // DEGUB temp calculation, munged for test!
  ByteToStr(level, txt4); // convert to string for display
  strLCD5XY(txt4, 0 , 3); // display on LCD in small font at 0,3
 
  // come here with 0 <= level <= 14
 
  for (i = 0; i == 13; i++)
  {
    if (level > i)
    {
      bargraph[i] = '#';
    }
    else
    {
      bargraph[i] = '-';
    }
  }
  strLCD5XY(bargraph, 0 , 5); // display on LCD in small font at 0,5
 
}

The idea is that in the loop [line 16] the characters in the string barcode get changed. In fact they stay with the initial values.

I'm going to check on something, because I think the original string may get put in ROM, which would explain why it doesn't work!

[jkmyoung]

So you're saying it always displays:
0123456789ABCD?


Besides initializing it to all full or all empty, could also break it into 2 for loops.

  for (i = 0; i <= level; i++) 
      bargraph[i] = '#'; 
  for (i = i; i <= 14; i++) 
      bargraph[i] = '-'; 
 

[nigelmercier]

@jkmyoung
All sorted. Thanks for giving me the idea where to look in the string library, I also discovered memset:

void upDisp(void)
{ // Update display
  char bargraph[15] = "              ";
  char reserve[15] =  "*RESERVE TANK*";
  byte level;
// set level here
  if (level == 0)
  {memcpy(bargraph, reserve, 14);}
  else
  {memset(bargraph, 0x5C, level);} // copy block characters into string
  strLCD5XY(bargraph, 0 , 5); // display on LCD in small font at 0,5

[nigelmercier]

[quote=nigelmercier;3549785]

for (i = 0; i == 13; i++)
//should be i <= 13 

I've also found the error in the loop, very surprised none of you guys spotted it!

For some reason I can't get it into my head that the second expression in a for statement is a while rather than a terminating condition! Must be all that BASIC I did in the 1970s.