如何将Pinescript时间输入匹配到正确Bar Index并修复趋势线绘制异常

线条缺失本质是Pine Script逐K线从左到右计算的特性导致的：在未运行到x2时间对应的K线时，你写的循环逻辑拿不到start_x2_bar的有效值，所以斜率、y值计算结果全为na，x1到x2区间的线条自然无法渲染。另外自定义循环匹配时间的方式性能差，还容易出现匹配偏差。

//@version=5
indicator("My Trend Line Script For Webhook", overlay=true)
    
start_x1_time = input.time(title="S Time/Profit #1", defval=(timestamp("06 Nov 2021 04:30 +0000")), inline = "start", group = "Start Position Trend Line", confirm=(true))  
start_y1 = input.price(title="", defval=0.2, inline = "start", group = "Start Position Trend Line", confirm=(true))
start_x2_time = input.time(title="S Time/Profit #2", defval=(timestamp("07 Nov 2021 04:30 +0000")), inline = "start2", group = "Start Position Trend Line", confirm=(true))
start_y2 = input.price(title="", defval=0.3, inline = "start2", group = "Start Position Trend Line", confirm=(true)) 

// 直接用内置函数匹配时间对应Bar索引，不需要循环
start_x1_bar = ta.valuewhen(time == start_x1_time, bar_index, 0)
start_x2_bar = ta.valuewhen(time == start_x2_time, bar_index, 0)

// 用var存储斜率和截距，计算一次永久生效
var float res_m = na
var float res_b = na
if not na(start_x1_bar) and not na(start_x2_bar)
    res_m := (start_y2 - start_y1) / (start_x2_bar - start_x1_bar)
    res_b := start_y1 - res_m * start_x1_bar

// 计算当前K线对应的趋势线y值，仅在x1-x2区间返回有效值
res_y = not na(res_m) and bar_index >= start_x1_bar and bar_index <= start_x2_bar ? res_m * bar_index + res_b : na

plot(res_y, color=color.red, title='Trendline Price Value', linewidth=1)

• 替换自定义循环逻辑，用Pine Script内置ta.valuewhen()函数直接匹配时间对应的Bar索引，准确率更高、性能更好
• 用var关键字存储斜率、截距计算结果，只要两个时间点的Bar索引都匹配成功就会永久存储有效值，不会受K线计算顺序影响，x1到x2区间的所有K线都能拿到正确的y值
• plot函数添加了显示范围限制，仅在bar_index处于x1和x2之间时渲染线条，避免区间外出现多余线条

内容的提问来源于stack exchange，提问作者Richard Barr