fitref.5 - Reflectivity Fitting for C-Plot

4-27-98  fitref.5.c has been updated, the following web page has also been updated to reflect those changes.
-- Michael Kelley
6-19-98  Three functions have been added to fitref.5:  pr - Prefilter, po - Postfilter, and p - Print.  They are self explanitory functions, so I won't add them to this page.
-- Mike
6-15-2005  Recent Adaptations have been made to the fitref function, in hopes that we may better fit our experimental data.
-- Clay Schumacher

1. The Main Program - Not much to say here.
2. The Setup Function - Prepares the program.
3. The Parameters - How are the parameters created. (What do the parameters mean?)
4. The Model - What is the model function and how is it used.
5. The Added Functions - These are the functions I have added.
1. Initialize Parameters
2. Save Parameters
3. Let (Set Parameter)
4. Vary Parameter
5. Print
6. Postfilter
7. Prefilter

#define X  (M_flag? Make_x[0]:dp->d_xx[0])

    I also removed many of the comments as I didn't think they helped understand the program more, but just were programming aids.

4-27-98  Four constants have been added: firstP, lastP, firstC, lastC to correspond to the first/last index values of each parameter.

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setup() {

 set_prompt(0, "FitRef (? for help)");  /* Main prompt */
 set_prompt(1, "FitRef");  /* Command-file prompt */

    And then assigns addresses to the parameter pointers (see The Parameters):

/* These next arrays are pointers to the parameters to make user defined
   functions easier to write */

 parameterP[1]=&p1;
 parameterP[2]=&p2;
 parameterP[3]=&p3;     etc...

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struct init_4 initial[] = {
       /* Name    Deriv? Fit?  Initial  Limit? Low  High */
        { "P(1)",   0,    0,       1,     0,    0,    0, },
        { "P(2)",   0,    1,       1,     1,  -88,   88, },
        { "P(3)",   0,    0,       1,     0,    0,    0, },
        { "P(4)",   0,    1,   0.334,     1,    0,    3, },
        { "P(5)",   0,    0,       0,     0,    0,    0, },
        { "P(6)",   0,    1,    17.5,     1,    0,  100, },
        { "P(7)",   0,    1,     .35,     1,    0,    3, },  etc.

(All these attributes are merely initial values and can be changed by the user, except for Deriv and Initial)

• Deriv - 0 because the analytic-derivative is not supplied.
• Fit - 0 for hold constant, 1 for variable.
• Initial - The initial value for the parameter.
• Limit - 0 for no limit, 1 for lower limit, 2 for upper limit, 3 for both.
• Low - The lower limit.
• High - The upper limit.

#define p1   fpar[0].p_b
#define fp1  fpar[0].p_fit
#define dp1  fpar[0].p_p

#define c1   fpar[28].p_b
#define fc1  fpar[28].p_fit
#define dc1  fpar[28].p_p

• p# (or c#) - the value of the parameter.
• fp# (or fc#) - the fit flag (0 for constant, 1 for variable).
• dp# (or dc#) - the analytic-derivative flag.

 parameterP[1]=&p1;
 parameterP[2]=&p2;
 parameterP[3]=&p3;
 parameterP[4]=&p4;
 parameterP[5]=&p5;
... etc. ...
 parameterC[5]=&c5;
 parameterC[6]=&c6;
 parameterC[7]=&c7;

What do the parameters mean?

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    My model() first declares two arrays, P and C, and lets these equal the parameters' current values:

 for (i=1; i<29; i++)
   P[i]=*parameterP[i];

 for (i=1; i<8; i++)
   C[i]=*parameterC[i];

    It then calculates the reflectivity using the function calculateReflec() which returns yfit, the value of the model.  X is the dependent variable from C-Plot:

 calculateReflec(P, C, X, &yfit);

calculateReflec() uses the same reflectivity function ref1.4.c uses.

4-27-98  The previous for statements now read:

 for (i=firstP; i<=lastP; i++)
   P[i]=*parameterP[i];

 for (i=firstC; i<=lastC; i++)
   C[i]=*parameterC[i];
 

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    First the function prototypes are declared.  C-Plot requires they be type int, but the value returned means nothing:

int initParam();
int setParam();
int newhelp();
int saveParam();
int varyParam();
void toggle(int *param, char name[]);

    Next they are assigned a mnemonic in the structure user_cmds[]:

 struct  user_cmds {
     char    c_one;                  /* The first letter of the command */
     char    c_two;                  /* The second letter (or 0) */
     int     (*c_func)();            /* The name of the function */
} user_cmds[] = {
     { 'i', 'p', initParam },
     { 'l', 't', setParam },
     { '?', '\0', newhelp },
     { 'S', 'P', saveParam },
     { 'v', 'a', varyParam },
     0,                              /* must be terminated with a zero */
};

• ip - Initialize Parameters:  Reads the parameters from a file.
• SP - Save Parameters:  Saves the parameters to a file readable by ip.
• lt - Let:  Changes the value of a parameter.
• va - Vary Parameter:  Toggles the vary flag for a parameter.
• ? - Displays a simple help screen.

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    First the variables are declared:

  FILE *inf;
  char ch, dummy, PfileName[255]="defaultparameters.dat";
  int n;       /* The array index */
  float val;   /* The array value */

    Next the function get_snum() is called to get the name of the file to open.  get_snum() is decribed in the C-Plot User Manual, Chapter 12:

  get_snum("Name of the parameter file to load", PfileName);

    It opens the file (unless there is an error).  I will not describe the file processing algorithm here, but the file syntax can be found in parameters.dat.

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    Define variables:

  char *cmd = get_cmdbuf();  /* This is a pointer to the command line */
  char name[21]="\0", par;
  double val;
  int n, i, len;

    cmd is a pointer to the command buffer, the string the user typed in to run the function.  If this string is longer than 3 characters then the name of a parameter must have been entered (hopefully).  E.g., compare these two ways of acessing the function:"lt c[7]=2" and "lt".  If there is one, it copies the command line parameter (the string minus the first three characters 'l', 't', and ' ') and finishes it with a null zero:

  if ((len=strlen(cmd))>3) {

    for (i=3; i<=len && i<20; i++)
      name[i-3] = cmd[i];      /* Copy the cmdline to the name array */
    name[i+1]='\0';

  } else {

    Else the user must now supply the command string (what parameter to change and what to change it to).  Inspecting this code and knowing that get_snum() returns a zero if the value of name is unchanged (in this case from "i.e. C[7]=4.0") reveals that if nothing is entered at the prompt, the function quits:

    strcpy(name, "i.e. C[7]=4.0");

    printf("\nYou MUST use the following format:  p[n]=val or p(n)=val.");
    printf("\n      Where p is the parameter, n is the index number, and val is the value.");
    printf("\n      IMPORTANT:  Do not add any spaces or other characters.");

    if (!get_snum("\nCommand string", name)) {
      printf("\nNo values changed.\n");
      return 0;
    }
  }

    Next, the parameter, index number, and new value is read from the command string with sscanf():

  if (name[1]=='[') sscanf(name, "%c[%d]=%lf", &par, &n, &val);
  if (name[1]=='(') sscanf(name, "%c(%d)=%lf", &par, &n, &val);

    If the index value and parameter is correct, the parameter is changed:

  switch (par) {
  case 'P':                                           /* This is the parameter P */
    if (n>0 && n<29)
      *parameterP[n]=val;
    else
      printf("I don't recognize or use %s.  Reason: Wrong index value.\n", name);
    break;

  case 'C':
    if (n>0 && n<8)
      *parameterC[n]=val;
    else
      printf("I don't recognize or use %s.  Reason: Wrong index value.\n", name);
    break;

  default:
      printf("I don't recognize or use %s.  Reason: Unrecognizable parameter.\n", name);
      break;
    }

4-27-98  The previous if statements now read:
  case 'P':                                           /* This is the parameter P */
    if (n>=firstP && n<lastP)
...
 case 'C':
    if (n>=firstC && n<lastC)

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    Define variables:

  FILE * of;
  char *cmd = get_cmdbuf();  /* A pointer to the commmand buffer used to call the function */
  char fileName[255]="parameters.dat";
  int i;
  double P[30], C[10];

    The default value of "parameters.dat" is assigned to fileName.

    If the length of cmd > 3, a file name must have been typed in (see Let), use this one.  Otherwise, prompt the user with get_snum() (see C-Plot User Manual Chapter 12 for a description of this function):

  if (strlen(cmd)>3)  /* There must be a file name typed */
    sscanf(cmd, "SP %s", fileName);
  else
    get_snum("What is the file name to save parameters to", fileName);

    Open the file, and print the parameters.

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    First define the variables as every good C programmer should:

  char *cmd = get_cmdbuf();  /* A pointer to the commmand buffer used to call the function */
  char name[21], par;
  int n, i, len;

    cmd is used the same way as in Save Parameters and Let.  If cmd > 3 assume there is a parameter to be changed in the command line.  Otherwise, prompt for one with get_snum() (which is found in the C-Plot User Manual Chapter 12):

 if ((len=strlen(cmd))>3) {   /* If length > 3 the user must have type a parameter into cmd */
    for (i=3; i<=len && i<20; i++)
      name[i-3] = cmd[i];      /* Copy the cmdline to the name array */
    name[i+1]='\0';

  } else {
    strcpy(name, "i.e. c(1)");

    printf("\nYou MUST use the following format:  p[n] or p(n).");
    printf("\n      Where n is a number and p is the parameter.");

    if (!get_snum("\nWhat is the parameter to toggle", name)) {
      printf("\nNo parameters toggled.\n");
      return 0;
    }
  }

    Get the parameter name and index value:

  name[0]=toupper(name[0]);

  if (name[1]=='[') sscanf(name, "%c[%d", &par, &n);
  if (name[1]=='(') sscanf(name, "%c(%d", &par, &n);

    Toggle its status using toggle():

  switch (par) {
  case 'P':                                           /* This is the parameter P */
      switch (n) {
        case 1: toggle(&fp1, name); break;
        case 2: toggle(&fp2, name); break;
        case 3: toggle(&fp3, name); break;

Toggle -
    A fairly simple function.  It makes param a pointer to the location of the fit flag (see The Parameters above) and changes it's truth:

void toggle(int *param, char name[])
{
  if (*param) {
    *param=0;
    printf("\n%s toggled from fit to constant.\n", name);
  } else {
    *param=1;
    printf("\n%s toggled from constant to fit.\n", name);
  }
}

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