1 files changed, 59 insertions, 0 deletions
diff --git a/structure/correlations/fit_knn.c b/structure/correlations/fit_knn.c
new file mode 100644
index 0000000..64fc4c3
--- /dev/null
+++ b/structure/correlations/fit_knn.c
@@ -0,0 +1,59 @@
+/**
+ * 
+ * Take a file which contains pairs in the form:
+ *
+ * k q
+ *
+ * compute qnn(k) and fit this function with a power-law
+ *
+ * a*x^{b}
+ *
+ * The fit is actually performed as a linear fit on the
+ * exponential-binned log-log distribution
+ *
+ *
+ */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <gsl/gsl_fit.h>
+#include "fit_utils.h"
+
+
+
+int main(int argc, char *argv[]){
+
+  double *k, *q, *x, *y;
+  int N, num;
+  double alpha;
+
+  double c0, c1, cov00, cov01, cov11, sqsum;
+
+  k=q=x=y=NULL;
+
+  if (argc < 3){
+    printf("%s <filein> <alpha>\n", argv[0]);
+    exit(1);
+  }
+  
+  alpha=atof(argv[2]);
+  
+  fprintf(stderr,"Alpha: %g\n", alpha);
+  
+  load_sequence_col(argv[1], &k, &N, 0);
+  load_sequence_col(argv[1], &q, &N, 1);
+  //exit(1);
+  exp_bin_avg(k, q, N, alpha, &x, &y, &num);
+  //normalize_distr(x, y, num);
+  //dump_distr(x, y, num);
+  compact_distr(x, y, &num);
+  //  dump_distr(x,y,num);
+  map_vec(x, num, log);
+  map_vec(y, num, log);
+  //dump_distr(x,y,num);
+
+  gsl_fit_linear(x, 1, y, 1, num, &c0, &c1, &cov00, &cov01, &cov11, &sqsum);
+  fprintf(stderr, "a: %g b: %g\n", exp(c0), c1);
+}