3.7. Usage of process-plugins

The example will show how to calculate Heart-Rate-Variability (HRV) using the process-plugin 'hrv'. We will perform the following steps:

• get 'hrv' plugin

• calculate HRV using the plugin

• print the calculation results

//
#include <stdio.h>
#include <ra.h>

int main(int argc, char *argv[])
{
    ra_handle ra;
    struct ra_info *inf;
    meas_handle meas;
    eval_handle eval;
    plugin_handle pl;
    struct proc_info *pi;

    /* initialize libRASCH */
    ra = ra_lib_init();
    if (ra == NULL)
    {
        printf("error initializing libRASCH\n");
        return -1;
    }

    /* open measurement */
    meas = ra_meas_open(ra, argv[1], 0);
    if (meas == NULL)
    {
        printf("can't open measurement %s\n", argv[1]);
        return -1;
    }

    /* get default evaluation */
    eval = ra_eval_get_def(meas);
    if (eval == NULL)
    {
        printf("no evaluation in measurement %s\n", argv[1]);
        return -1;
    }

    /* get plugin-handle for hrv-plugin */
    pl = ra_plugin_get_by_name(ra, "hrv", 0); 
    if (pl == NULL)
    {
        printf("can't find plugin 'hrv'\n");
        return -1;
    }

    /* calculate hrv-values using the hrv-plugin */
    pi = (struct proc_info *)ra_proc_get(pl); 
    pi->mh = meas;
    pi->rh = ra_rec_get_first(meas, 0);
    pi->eh = eval;
    if (ra_proc_do(pi) == 0) 
    {
        long num_results, l;
        value_handle vh;

        /* get number of results */
        vh = ra_value_malloc();
        if (ra_info_get(pl, RA_INFO_PL_NUM_RESULTS_L, vh) != 0)
        {
            printf("no results\n");
            return -1;
        }
        num_results = ra_value_get_long(vh);

        for (l = 0; l < num_results; l++)
        {
            char out[200], t[100];

            /* set number of result in which we are interested */
            ra_value_set_number(vh, l); 

            /* test if result is a default value (some
               non-default results are arrays which we skip in
               this example) */
            ra_info_get(pl, RA_INFO_PL_RES_DEFAULT_L, vh);
            if (ra_value_get_long(vh) == 0)
                continue;

            out[0] = '\0';
            if (ra_info_get(pl, RA_INFO_PL_RES_NAME_C, vh) == 0)
            {
                strcpy(t, ra_value_get_string(vh));
                strcat(out, t);
            }
            if (ra_info_get(pl, RA_INFO_PL_RES_DESC_C, vh) == 0)
            {
                sprintf(t, " (%s)", ra_value_get_string(vh));
                strcat(out, t);
            }
            if (ra_proc_get_result(pi, vh) == 0) 
            {
                sprintf(t, ": %lf", ra_value_get_double(vh));
                strcat(out, t);
            }

            printf("%s\n", out);
        }

        ra_value_free(vh);
    }

    /* close */
    ra_proc_free(pi);
    ra_meas_close(meas);
    ra_lib_close(ra);

    return 0;
}                               /* main() */

//

The output of the above example for the ECG '100s' is shown here:

SDNN (standard deviation of normal-to-normal intervals):
30.876196
HRVI (HRV-Index): 4.800000
SDANN (standard deviation of averaged normal-to-normal
intervals): nan
rmssd (root mean of squared sucsessive differences): 33.839537
pNN50 (): 7.142857
TP (total power): 482.603096
ULF (ultra low frequency power): 0.000000
VLF (very low frequency power of short-term recordings):
32.889150
LF (low frequency power): 157.213726
LF_NORM (normalised low frequency power): 34.958606
HF (high freuqency power): 292.500220
HF_NORM (normalised high frequency power): 65.041394
LF_HF_RATIO (LF/HF ratio): 0.537482
POWER_LAW (power law behavior): 0.000000