fixed the computation of the standard deviation on iterables

Author: v923z

code/numpy/numerical/numerical.c

@@ -67,16 +67,10 @@ static mp_obj_t numerical_sum_mean_std_iterable(mp_obj_t oin, uint8_t optype, si
     size_t count = 0;
     mp_obj_iter_buf_t iter_buf;
     mp_obj_t item, iterable = mp_getiter(oin, &iter_buf);
-    if((item = mp_iternext(iterable)) != MP_OBJ_STOP_ITERATION) {
-        value = mp_obj_get_float(item);
-        sum += value;
-        M = m = value;
-        count++;
-    }
     while((item = mp_iternext(iterable)) != MP_OBJ_STOP_ITERATION) {
         value = mp_obj_get_float(item);
         sum += value;
-        m = M + (value - M) / count;
+        m = M + (value - M) / (count + 1);
         s = S + (value - M) * (value - m);
         M = m;
         S = s;
@@ -87,7 +81,7 @@ static mp_obj_t numerical_sum_mean_std_iterable(mp_obj_t oin, uint8_t optype, si
     } else if(optype == NUMERICAL_MEAN) {
         return count > 0 ? mp_obj_new_float(m) : mp_obj_new_float(MICROPY_FLOAT_CONST(0.0));
     } else { // this should be the case of the standard deviation
-        return count > ddof ? mp_obj_new_float(MICROPY_FLOAT_C_FUN(sqrt)(count * s / (count - ddof))) : mp_obj_new_float(MICROPY_FLOAT_CONST(0.0));
+        return count > ddof ? mp_obj_new_float(MICROPY_FLOAT_C_FUN(sqrt)(s / (count - ddof))) : mp_obj_new_float(MICROPY_FLOAT_CONST(0.0));
     }
 }
 

code/ulab.c

@@ -24,9 +24,6 @@
 #include "ndarray.h"
 #include "ndarray_properties.h"
 
-#if CIRCUITPY
-#include "circuitpy/vector/vector.h"
-#else
 #include "numpy/numpy.h"
 #include "scipy/scipy.h"
 #include "numpy/fft/fft.h"
@@ -37,7 +34,7 @@
 
 #include "user/user.h"
 
-#define ULAB_VERSION 2.1.3
+#define ULAB_VERSION 2.1.5
 #define xstr(s) str(s)
 #define str(s) #s
 #define ULAB_VERSION_STRING xstr(ULAB_VERSION) xstr(-) xstr(ULAB_MAX_DIMS) xstr(D)

docs/ulab-change-log.md

@@ -1,3 +1,9 @@
+Fri, 29 Jan 2021
+
+version 2.1.5
+
+    fixed error, when calculating standard deviation of iterables
+
 Thu, 21 Jan 2021
 
 version 2.1.3