Question

我有一个数据列表（两列），我想在gnuplot中仅绘制第二列具有局部最大值的值。

为此，我想看看第i行的第二列是否大于第（i-1）行和第（i + 1）行。

Answer 1

它可以完成，我很无聊，这样做。我生成了以下一组随机数据：

根据列表中的位置绘制值如下所示：

enter image description here

您可以从上图中发现局部最大值。现在我可以在临时变量中处理存储前两个值（x和y坐标）的数据点，当我确定最大值时，我绘制数据点：

# Select the columns of your data file that contain x and y data
# (usually 1 and 2 respectively)
xcolumn=0
ycolumn=1

plot "data" u (column(xcolumn)):(column(ycolumn)) w l, \
"data" u (column(0)==0 ? (last2y=column(ycolumn), \
last2x=column(xcolumn), 1/0) : column(0)==1 ? (lasty=column(ycolumn), \
lastx=column(xcolumn), 1/0) : lastx) \
: \
( column(0) < 2 ? 1/0 : (last2y < lasty && \
column(ycolumn) < lasty) ? (value=lasty, last2y=lasty, last2x=lastx, \
lasty=column(ycolumn), lastx=column(xcolumn), value) : (last2y=lasty, \
last2x=lastx, lasty=column(ycolumn), lastx=column(xcolumn), 1/0)) pt 7

enter image description here

Answer 2

简单的gnuplot峰查找器

比较3个连续的数据点是查找最大值/峰值的简单方法。

if y(i-1) < y(i) > y(i+1) then you have a maximum/peak at x(i).

但是，如果您有嘈杂的曲线（通常像实验光谱那样），您将获得太多的“峰值”。

以下gnuplot代码允许为被认为是峰值的阈值设置阈值。该代码基本上为每个峰计算一个数，该数是对峰“独立性”的度量。（请参见https://en.wikipedia.org/wiki/Topographic_prominence）。该代码使用数据块，因此需要gnuplot> = 5.2。欢迎评论和改进。

测试数据： Spectrum.dat

# x    y
6.02   153.33
9.59   154.03
9.59   154.03
9.59   154.03
9.83   153.66
10.58   153.22
10.62   153.85
11.32   152.33
11.53   153.67
11.88   153.27
13.28   153.97
13.42   154.35
14.56   152.99
14.75   153.50
15.23   153.91
15.59   153.58
16.56   153.85
16.70   154.49
16.97   153.98
17.23   154.49
17.37   153.73
17.90   154.24
17.93   154.91
18.80   154.23
18.83   154.64
20.37   153.59
20.48   153.99
21.70   153.19
22.29   154.36
22.41   153.38
23.34   155.04
23.41   155.38
24.38   154.71
24.58   154.96
25.40   155.13
25.41   154.70
26.20   154.21
26.36   154.84
26.55   154.11
26.79   154.73
27.02   154.13
27.54   154.51
27.55   155.17
28.08   155.42
28.33   154.97
28.61   155.17
29.06   155.10
29.12   154.26
29.61   153.61
30.03   154.84
30.58   155.30
30.68   154.72
31.21   155.82
31.99   155.83
32.58   156.56
33.03   156.23
33.51   156.79
33.73   158.88
34.00   157.85
34.17   159.82
34.32   161.24
34.55   160.78
34.85   162.58
35.14   163.84
35.50   168.07
35.85   168.40
36.55   180.70
36.75   179.27
37.16   178.78
38.15   168.93
38.29   170.52
38.83   164.96
39.63   161.39
40.17   158.67
40.48   159.22
40.88   159.75
40.95   158.77
41.45   160.86
41.58   160.33
41.84   161.12
42.51   162.83
43.33   165.09
43.43   164.20
43.63   164.56
44.22   164.76
44.92   162.58
45.71   159.40
45.98   159.84
47.03   157.01
47.53   157.15
47.95   155.48
48.08   156.21
48.56   154.51
48.64   155.11
49.14   153.69
49.31   154.27
49.86   154.71
50.14   154.13
50.33   155.83
50.37   155.36
51.00   154.60
51.37   154.75
52.00   154.91
52.01   154.34
54.28   153.83
54.46   154.33
54.83   153.19
55.58   155.30
55.86   154.95
55.92   156.48
56.40   155.89
56.59   155.16
57.56   155.96
57.64   155.21
58.31   155.36
58.38   156.08
58.92   155.84
59.00   155.28
59.57   155.96
59.94   155.37
61.31   156.07
61.32   156.78
61.96   157.34
62.37   156.89
63.14   159.45
63.54   159.51
63.80   161.03
63.93   161.56
64.17   161.12
64.84   162.38
65.14   166.28
65.64   168.07
66.22   169.06
66.42   167.70
66.56   168.40
67.10   167.20
67.24   168.00
67.77   166.82
68.04   165.80
68.15   166.88
68.43   164.98
68.86   166.28
69.33   166.55
70.43   179.11
70.93   198.16
71.62   208.09
72.01   216.42
72.43   223.37
72.79   226.74
72.84   231.24
73.07   229.85
73.15   222.04
73.32   224.49
73.58   211.26
73.71   215.36
73.98   201.60
73.98   208.75
74.25   202.93
74.53   189.70
74.90   184.01
75.18   184.80
76.67   173.29
77.05   173.82
77.15   170.94
77.27   177.13
77.52   175.20
77.70   179.76
78.17   179.96
78.36   183.33
78.73   187.05
78.86   184.67
79.03   189.90
79.38   189.70
79.59   190.62
79.88   189.17
80.59   186.52
80.60   183.61
81.26   177.53
81.67   173.69
82.07   173.69
82.90   165.37
83.94   164.04
84.25   164.42
85.01   161.26
85.22   162.18
85.77   161.19
85.89   159.97
86.46   160.72
86.56   161.78
87.06   160.56
87.19   161.53
87.74   159.60
87.89   160.64
88.30   158.74
88.56   159.27
88.98   158.08
89.25   158.70
90.12   159.15
90.14   158.34
90.99   159.59
91.06   158.86
91.72   159.01
91.74   158.48
92.43   157.68
92.48   158.34
93.15   157.68
93.54   158.34
93.72   157.61
94.20   158.00
94.39   158.64
94.82   157.83
95.00   158.40
95.43   156.77
95.66   157.39
95.81   155.44
95.84   156.25
96.53   157.70
96.55   156.70
97.22   159.14
97.47   158.13
97.53   156.75
98.57   157.83
98.85   157.40
98.92   158.45
99.35   158.25
99.40   157.77
100.04   158.33
100.14   157.91
101.00   158.30
101.04   157.80
101.94   157.48
102.02   158.20
102.53   156.56
102.58   157.84
103.23   157.75
103.38   156.82
103.39   158.93
103.75   158.60
104.05   159.26
104.30   158.14
104.55   158.56
104.85   157.15
105.17   160.09
105.21   158.41
105.52   161.78
105.80   160.00
105.92   160.86
106.11   159.54
106.31   159.93
106.86   160.99
107.20   160.88
107.42   162.05
107.62   160.33
107.80   161.16
108.39   159.90
108.79   162.25
109.08   161.85
109.46   163.77
109.73   163.42
109.96   165.16
111.02   170.08
111.30   173.56
111.69   173.56
112.35   180.08
112.61   189.04
112.89   193.53
113.28   193.67
113.81   210.73
113.94   206.63
114.20   213.11
114.46   219.60
115.00   230.44
115.12   236.95
115.27   234.68
115.78   238.78
116.11   239.57
116.40   238.51
116.43   239.90
117.90   230.31
118.18   221.32
118.42   222.51
118.70   217.48
118.83   211.13
119.25   210.34
119.37   204.51
119.65   205.18
120.08   200.28
120.12   198.96
120.84   204.18
120.95   201.87
121.24   206.49
121.50   203.01
121.64   204.44
121.73   201.74
121.84   202.53
122.14   203.72
122.19   202.40
122.44   203.59
122.45   204.91
122.64   201.61
122.76   203.17
123.08   200.79
123.10   200.15
123.34   199.51
123.39   200.81
123.88   200.28
124.25   196.58
124.26   194.06
124.53   193.67
125.18   188.77
125.81   182.16
126.10   182.55
127.32   171.71
127.70   171.18
127.96   168.27
128.22   168.66
128.62   165.71
128.89   166.24
129.30   163.94
129.56   164.47
129.96   162.22
130.21   162.72
130.53   160.83
130.93   160.61
131.15   161.24
131.84   160.06
131.93   161.12
132.71   159.87
133.06   163.17
133.38   162.73
134.17   166.97
134.31   172.37
134.85   180.83
135.38   193.01
135.62   190.09
135.64   200.81
135.75   204.05
136.16   206.10
136.80   200.22
137.21   199.36
138.29   175.41
138.56   176.73
139.98   163.09
140.03   161.92
140.32   164.53
140.55   163.80
140.85   166.25
141.24   165.81
141.45   167.92
141.59   166.51
141.99   170.65
142.25   170.19
142.76   177.79
142.91   174.95
143.72   187.66
143.79   185.37
144.65   179.11
144.91   180.32
145.71   175.74
145.84   174.80
146.54   177.73
146.74   180.57
147.30   181.11
147.42   180.30
148.33   181.23
148.38   180.68
148.93   181.19
149.09   181.74
149.24   178.43
149.49   179.03
149.96   174.55
150.69   173.48
151.83   168.06
151.89   169.39
152.41   168.27
152.96   169.45
153.02   168.53
153.47   169.42
153.71   168.78
153.91   169.44
154.08   167.74
154.54   168.92
154.65   168.20
155.61   168.79
156.78   165.75
157.06   166.08
157.54   162.68
157.84   163.40
158.51   162.73
158.57   161.85
159.45   161.27
159.57   160.33
160.11   158.81
160.24   159.81
160.90   159.27
160.90   158.08
161.17   158.48
161.43   158.10
161.59   158.72
161.83   157.91
162.44   158.48
162.61   157.94
163.41   158.75
163.43   158.19
163.94   158.99
163.96   158.33
164.60   158.23
164.87   158.74
165.81   158.50
166.10   158.08
166.74   158.91
167.02   158.48
167.67   159.68
167.96   159.28
168.90   159.81
168.96   160.34
169.57   159.77
169.76   161.28
170.00   160.75
171.01   163.77
171.12   163.13
171.79   163.71
172.83   169.14
173.19   169.13
173.52   171.06
173.73   170.38
173.87   171.65
174.27   171.90
174.41   175.94
174.94   177.39
175.20   183.48
175.71   185.07
175.84   190.49
176.48   193.27
176.51   196.84
177.34   201.47
177.62   207.30
177.69   205.18
177.87   203.26
178.08   204.46
178.45   199.43
178.76   199.62
179.02   193.53
179.43   192.08
179.96   178.98
180.21   176.40
180.56   176.57
180.57   176.20
181.14   176.43
181.24   175.51
181.68   174.93
181.74   177.13
181.97   178.85
182.05   176.93
182.14   179.78
182.30   177.53
182.59   178.72
182.72   176.93
183.04   177.67
183.21   178.76
183.33   177.92
183.75   179.99
184.06   179.78
184.28   182.07
184.71   182.49
185.40   187.78
185.61   184.01
186.02   183.86
186.20   180.07
186.79   178.72
186.97   175.44
187.34   175.15
188.45   167.65
188.84   166.25
189.08   166.77
189.50   164.08
189.90   163.69
189.92   161.67
190.37   162.04
190.41   162.90
190.90   161.40
190.93   162.58
192.29   159.27
192.33   158.79
193.23   160.21
193.34   159.73
193.78   161.15
194.07   160.20
194.54   160.43
194.93   159.64
195.39   159.82
195.98   160.86
196.08   160.05
196.45   161.78
197.00   158.90
197.03   159.95
197.70   157.15
198.07   160.13
198.10   158.48
198.83   159.67
198.85   160.46
199.27   159.80
199.46   159.46
200.46   161.78
200.73   161.38
201.38   162.37
201.92   159.72
202.06   160.52
203.14   157.67
203.52   157.95
203.93   157.02
204.13   157.55
204.39   156.66
204.63   157.15
206.35   155.53
206.57   156.00
207.21   156.57
207.33   155.76
208.23   157.93
208.52   157.68
208.92   157.15
209.21   157.56
209.41   156.62
209.88   156.89
211.48   154.50
211.70   155.00
212.39   155.37
212.51   154.53
212.84   154.31
212.92   155.17
213.26   154.38
213.44   155.24
213.70   154.57
214.15   154.97
214.24   155.71
215.55   155.20
215.65   156.01
216.28   156.16
216.55   156.87
216.73   155.56
216.95   156.23
217.25   156.03
217.47   155.46
217.93   155.50
218.26   155.83
218.56   155.04
219.31   154.73
219.97   154.72
220.10   155.61
220.79   154.23
220.87   154.94
221.87   154.64
222.07   154.12
222.58   154.47
222.69   155.02
223.21   154.51
223.24   155.22
223.86   154.54
223.90   155.22
224.48   154.29
224.54   155.04
225.22   154.73
225.28   153.86
225.54   154.13
225.76   154.72
225.84   153.93
226.52   154.23
226.60   154.94
226.98   154.02
227.78   153.89
228.29   154.67
228.62   154.29
229.12   154.90
229.46   154.16
229.83   154.48
230.28   153.54
230.50   154.06
230.91   153.03
231.18   153.63
231.79   153.99
231.97   153.45
232.70   154.86

代码：

### a simple gnuplot peak-finder
# requires gnuplot >=5.2
reset session

FILE = "Spectrum.dat"
set table $Data
    plot FILE u 1:2 with table
unset table

ColX=1
ColY=2

# extract all peaks
y2=y1=NaN
set print $Peaks
do for [i=2:|$Data|-1] {
    if ( word($Data[i-1],ColY)<word($Data[i],ColY) && word($Data[i+1],ColY)<word($Data[i],ColY) ) \
    { print sprintf("%d %s %s", i, word($Data[i],ColX), word($Data[i],ColY)) }
}
set print

# determine prominence
set print $PeakInfo
do for [i=1:|$Peaks|] {
    PeakIndex = int(word($Peaks[i],1))
    PeakX = real(word($Data[PeakIndex],ColX))
    PeakY = real(word($Data[PeakIndex],ColY))
    MinY1 = PeakY
    do for [j=PeakIndex+1:|$Data|] {   # search for higher peak to the right
        if ( word($Data[j],ColY) > PeakY ) { break }
        else { MinY1 = word($Data[j],ColY) < MinY1 ? word($Data[j],ColY) : MinY1 }
    }
    MinY2 = PeakY
    do for [j=PeakIndex-1:1:-1] {      # search for higher peak to the left
        if ( word($Data[j],ColY) > PeakY ) { break }
        else { MinY2 = word($Data[j],ColY) < MinY2 ? word($Data[j],ColY) : MinY2 }
    }
    Prominence = MinY1 > MinY2 ? PeakY-MinY1 : PeakY-MinY2
    NormalizedProminence = 100.*Prominence/PeakY
    print sprintf("%2 d %6 .1f %6 .1f %6 .2f", i, PeakX, PeakY, NormalizedProminence )
}
set print 
# print $PeakInfo

set yrange[150:250]
Threshold = 2.4
set label 1 at graph 0.05, 0.9 sprintf("Threshold: %g",Threshold)
plot $Data u 1:2 w lp pt 7 ps 0.5 lc rgb "red" not, \
     $PeakInfo u ($4>Threshold?$2:NaN):3 w p pt 7 lc rgb "blue" not, \
     $PeakInfo u ($4>Threshold?$2:NaN):3:2 w labels offset 0,0.8 not, \
     $PeakInfo u ($4>Threshold?$2:NaN):3 w impulses lc rgb "black" not
### end of code

结果：（用于不同的阈值）

在gnuplot中查找本地最大数据文件

2 个答案:

简单的gnuplot峰查找器