Is this what you mean?
library(tidyverse)
library(broom)
# Sample data from file
url <- "https://raw.githubusercontent.com/MohJumper/VisualAuditoryModality/master/new_by_particip.csv"
download.file(url, "data.csv")
df <- read.csv("data.csv")
df %>%
group_nest(Source.Name, visbility, soundvolume) %>%
mutate(model = map(data, ~lm(m ~ stim_ending_t, data = .x))) %>%
mutate(slope = map_dbl(model, ~tidy(.x)$estimate[2]))
#> # A tibble: 63 x 6
#> Source.Name visbility soundvolume data model slope
#> <fct> <int> <int> <list> <lis> <dbl>
#> 1 001_visual_demo1.csv 0 0 <tibble [12 × … <lm> 0.485
#> 2 001_visual_demo1.csv 0 1 <tibble [12 × … <lm> 0.518
#> 3 001_visual_demo1.csv 1 0 <tibble [12 × … <lm> 0.612
#> 4 002_visual_demo1.csv 0 0 <tibble [12 × … <lm> 0.691
#> 5 002_visual_demo1.csv 0 1 <tibble [12 × … <lm> 0.704
#> 6 002_visual_demo1.csv 1 0 <tibble [12 × … <lm> 0.783
#> 7 003_visual_demo1.csv 0 0 <tibble [12 × … <lm> 0.539
#> 8 003_visual_demo1.csv 0 1 <tibble [12 × … <lm> 0.428
#> 9 003_visual_demo1.csv 1 0 <tibble [12 × … <lm> 0.458
#> 10 003demo_visual_demo1.… 0 0 <tibble [12 × … <lm> 0.514
#> # … with 53 more rows
Created on 2019-07-25 by the reprex package (v0.3.0.9000)
Each topic here must be about one defined issue, I recommend you to solve your first issue and then ask this question on a new topic providing a REPRoducible EXample (reprex) and making clear what kind of graph you want to do and which are the variables you want to plot.