我在txt 文件中有數(shù)據(jù)，我將其轉(zhuǎn)換為數(shù)據(jù)幀（data3），我將索引重命名為從 -6 到 +5，現(xiàn)在，在 for 循環(huán)中，我想使用訪問數(shù)據(jù)幀的特定值iloc 命令，但我沒有得到正確的值。數(shù)據(jù)框看起來像這樣如果我使用 data3.iloc[-6,1] 我期望返回值 = -6 但相反，我得到 -20data3.iloc[-5,1] 我原本期待=-20，但結(jié)果卻是-6data3.iloc[-4,1] 我原以為 = -28 但結(jié)果是 -7有人可以幫我嗎？將索引保留在 -6 到 +5 之間對我來說很重要這是我的代碼。謝謝import numpy as npimport pandas as pddata= pd.read_csv('perfilprueba.txt',delimiter=' ')## This is because when I read the txt doesnt read dist and amp as diferent columnsdata_drop = data.drop(data.columns[[1, 2, 3, 4, 6,7]], axis=1) data2=data_drop.rename(columns={"Unnamed: 5": "amp"})## These are two index I will use laterm=int(round(len(data2.index)))n=int(round(m/2))## This is because I wanted that my data had index values from -6 to 5+ AND## also a column with values from -6 to +5r = pd.Series(np.linspace(-n, n-1,m)) data2['r'] = r erre = pd.Series(np.linspace(-n, n-1,m)) data2['erre']=erre data3=data2.set_index('r')## Now I want to run a for loop## that returns me the values of the "amp" column as r moves from -6 to +5ap=[]for r in range(-n,n): a = data3.loc[[r],['amp']] ap += [a]
2 回答
鳳凰求蠱
TA貢獻(xiàn)1825條經(jīng)驗(yàn) 獲得超4個贊
pandas.DataFrame.iloc是“基于純整數(shù)位置的索引，用于按位置選擇”，這意味著當(dāng)您調(diào)用 時(shí)data3.iloc[-5, 1]，您實(shí)際上是從數(shù)據(jù)幀末尾的第五行的第二列中獲取。
在你的情況下，我會使用pandas.DataFrame.at，盡管在這種情況下，你也可以使用pandas.DataFrame.loc.
該腳本如下所示：
# reading the data (the "sep=\s+" parameter does what is needed)
data3 = pd.read_csv('perfilprueba.txt', sep="\s+")
m = int(round(len(data3.index)))
n = int(round(m/2))
# changing the index so it starts at -n
data3.index -= n
data3['erre'] = data3.index
ap = []
for r in range(-n,n):
? ? # note that you have to use the column name here
? ? a = data3.at[r,"amp"]
? ? ap.append(a)
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