Repository: hidrokit/hidrokit

Issue:
bug: timeseries.timestep_table error saat menggunakan keep_first
### Sistem
* Versi hidrokit: 0.4.0
* Distribusi python:
```
::       python version: 3.7.7     
::        numpy version: 1.18.5    
::       pandas version: 1.0.5     
::   matplotlib version: 3.2.2     
::     hydroerr version: 1.24      
::     hidrokit version: 0.4.0     
::   tensorflow version: 2.1.0     
::        keras version: 2.2.4-tf
```
* Sistem operasi: Windows 10

### Ringkasan Permasalahan

Keluaran menggunakan `keep_first=False` tidak sesuai harapan

__jika menggunakan True__
![image](https://user-images.githubusercontent.com/1007910/87144619-3ec15600-c2d2-11ea-99d8-b8398540008f.png)

__jika menggunakan False__
![image](https://user-images.githubusercontent.com/1007910/87144713-66b0b980-c2d2-11ea-8c71-9aa4ad7c8c2b.png)

Seharusnya, nilai `ch_A_tmin1` bernilai `4.18994`

__tabel 8 baris pertama__
![image](https://user-images.githubusercontent.com/1007910/87144787-8811a580-c2d2-11ea-8644-d4cd640b9430.png)


Comments:

Patch:
diff --git a/CITATION.cff b/CITATION.cff
index caf5fad..550bb8c 100644
--- a/CITATION.cff
+++ b/CITATION.cff
@@ -9,6 +9,6 @@ date-released: 2020-01-15
 doi: 10.5281/zenodo.3276220
 license: MIT
 message: "Jika menggunakan perangkat lunak ini, mohon sitasi menggunakan metadata ini."
-repository-code: "https://github.com/taruma/hidrokit"
+repository-code: "https://github.com/hidrokit/hidrokit"
 title: "hidrokit: Analisis Hidrologi dengan Python"
-version: "0.3.5"
+version: "0.3.6"
diff --git a/hidrokit/__version__.py b/hidrokit/__version__.py
index f033401..27e660b 100644
--- a/hidrokit/__version__.py
+++ b/hidrokit/__version__.py
@@ -1,4 +1,4 @@
-VERSION = (0, 3, 5)
+VERSION = (0, 3, 6)
 DEV_STATUS = ""
 
 __version__ = '.'.join(map(str, VERSION)) + DEV_STATUS
diff --git a/hidrokit/prep/timeseries.py b/hidrokit/prep/timeseries.py
index fa2bb42..85e8720 100644
--- a/hidrokit/prep/timeseries.py
+++ b/hidrokit/prep/timeseries.py
@@ -34,7 +34,7 @@ def _timestep_single(array, index=0, timesteps=2, keep_first=True):
         x.append(array[start:end, index])
 
     if not keep_first:
-        x.pop(-1)
+        x.pop(0)
 
     return np.array(x).transpose()
 


Test patch:
diff --git a/tests/test_prep_timeseries.py b/tests/test_prep_timeseries.py
index 95efa7b..4a69894 100644
--- a/tests/test_prep_timeseries.py
+++ b/tests/test_prep_timeseries.py
@@ -83,9 +83,9 @@ def test__timestep_multi():
     # Argument: timesteps=4, keep_first=False
     array_result_3 = np.array(
         [
+            [40, 30, 20, 10, 43, 33, 23, 13, 45, 35, 25, 15],
             [50, 40, 30, 20, 53, 43, 33, 23, 55, 45, 35, 25],
-            [60, 50, 40, 30, 63, 53, 43, 33, 65, 55, 45, 35],
-            [70, 60, 50, 40, 73, 63, 53, 43, 76, 65, 55, 45]
+            [60, 50, 40, 30, 63, 53, 43, 33, 65, 55, 45, 35]
         ]
     )
 
@@ -152,9 +152,9 @@ def test_timestep_table():
                  'C_tmin1', 'C_tmin2', 'C_tmin3', 'C_tmin4'],
         data=np.array(
             [
+                [40, 30, 20, 10, 43, 33, 23, 13, 45, 35, 25, 15],
                 [50, 40, 30, 20, 53, 43, 33, 23, 55, 45, 35, 25],
-                [60, 50, 40, 30, 63, 53, 43, 33, 65, 55, 45, 35],
-                [70, 60, 50, 40, 73, 63, 53, 43, 76, 65, 55, 45]
+                [60, 50, 40, 30, 63, 53, 43, 33, 65, 55, 45, 35]
             ]
         )
     )