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Use extract_xxx functions

We first created a mass_dataset class object.

library(massdataset)
library(tidyverse)

data("expression_data")
data("sample_info")
data("sample_info_note")
data("variable_info")
data("variable_info_note")

object =
  create_mass_dataset(
    expression_data = expression_data,
    sample_info = sample_info,
    variable_info = variable_info,
    sample_info_note = sample_info_note,
    variable_info_note = variable_info_note
  )
  
object
#> -------------------- 
#> massdataset version: 0.99.1 
#> -------------------- 
#> 1.expression_data:[ 1000 x 8 data.frame]
#> 2.sample_info:[ 8 x 4 data.frame]
#> 8 samples:Blank_3 Blank_4 QC_1 ... PS4P3 PS4P4
#> 3.variable_info:[ 1000 x 3 data.frame]
#> 1000 variables:M136T55_2_POS M79T35_POS M307T548_POS ... M232T937_POS M301T277_POS
#> 4.sample_info_note:[ 4 x 2 data.frame]
#> 5.variable_info_note:[ 3 x 2 data.frame]
#> 6.ms2_data:[ 0 variables x 0 MS2 spectra]
#> -------------------- 
#> Processing information
#> 1 processings in total
#> create_mass_dataset ---------- 
#>       Package         Function.used                Time
#> 1 massdataset create_mass_dataset() 2026-03-02 09:27:54

In massdataset package, there are a series of functions named as extract_xxx(), users can use them to extract data from mass_dataset calss object.

##sample_info
extract_sample_info(object)
#>   sample_id injection.order   class   group
#> 1   Blank_3               1   Blank   Blank
#> 2   Blank_4               2   Blank   Blank
#> 3      QC_1               3      QC      QC
#> 4      QC_2               4      QC      QC
#> 5     PS4P1               5 Subject Subject
#> 6     PS4P2               6 Subject Subject
#> 7     PS4P3               7 Subject Subject
#> 8     PS4P4               8 Subject Subject
##variable_info
extract_variable_info(object) %>% head()
#>     variable_id        mz        rt
#> 1 M136T55_2_POS 136.06140  54.97902
#> 2    M79T35_POS  79.05394  35.36550
#> 3  M307T548_POS 307.14035 547.56641
#> 4  M183T224_POS 183.06209 224.32777
#> 5   M349T47_POS 349.01584  47.00262
#> 6  M182T828_POS 181.99775 828.35712
##expression_data
extract_expression_data(object) %>% head()
#>               Blank_3 Blank_4      QC_1      QC_2     PS4P1     PS4P2   PS4P3
#> M136T55_2_POS      NA      NA 1857924.8 1037763.8 1494436.1 3496912.1 1959179
#> M79T35_POS         NA      NA 2821550.2 1304875.3 2471336.1 3333582.7 2734244
#> M307T548_POS       NA      NA  410387.6  273687.8  288590.2  137297.5      NA
#> M183T224_POS       NA      NA        NA        NA        NA 5059068.1 5147422
#> M349T47_POS        NA      NA 8730104.8 4105598.5 5141073.2 8424315.6 7896633
#> M182T828_POS  3761893 2572593        NA 3662819.1 5700534.8 4600172.4 5557015
#>                   PS4P4
#> M136T55_2_POS 1005418.8
#> M79T35_POS    3361452.3
#> M307T548_POS   271318.3
#> M183T224_POS         NA
#> M349T47_POS   6441449.0
#> M182T828_POS  4433034.2
##sample_info_note
extract_sample_info_note(object) 
#>              name         meaning
#> 1       sample_id       sample_id
#> 2 injection.order injection.order
#> 3           class           class
#> 4           group           group
##variable_info_note
extract_variable_info_note(object) 
#>          name     meaning
#> 1 variable_id variable_id
#> 2          mz          mz
#> 3          rt          rt
##ms2_data
extract_ms2_data(object)
#> list()
##process_info
extract_annotation_table(object)
#> data frame with 0 columns and 0 rows
##process_info
extract_process_info(object)
#> $create_mass_dataset
#> -------------------- 
#> pacakge_name: massdataset 
#> function_name: create_mass_dataset() 
#> time: 2026-03-02 09:27:54.550095 
#> parameters:
#> no : no

Use slot()

slot(object = object, name = "sample_info")
#>   sample_id injection.order   class   group
#> 1   Blank_3               1   Blank   Blank
#> 2   Blank_4               2   Blank   Blank
#> 3      QC_1               3      QC      QC
#> 4      QC_2               4      QC      QC
#> 5     PS4P1               5 Subject Subject
#> 6     PS4P2               6 Subject Subject
#> 7     PS4P3               7 Subject Subject
#> 8     PS4P4               8 Subject Subject
slot(object = object, name = "variable_info") %>% head()
#>     variable_id        mz        rt
#> 1 M136T55_2_POS 136.06140  54.97902
#> 2    M79T35_POS  79.05394  35.36550
#> 3  M307T548_POS 307.14035 547.56641
#> 4  M183T224_POS 183.06209 224.32777
#> 5   M349T47_POS 349.01584  47.00262
#> 6  M182T828_POS 181.99775 828.35712
slot(object = object, name = "expression_data") %>% head()
#>               Blank_3 Blank_4      QC_1      QC_2     PS4P1     PS4P2   PS4P3
#> M136T55_2_POS      NA      NA 1857924.8 1037763.8 1494436.1 3496912.1 1959179
#> M79T35_POS         NA      NA 2821550.2 1304875.3 2471336.1 3333582.7 2734244
#> M307T548_POS       NA      NA  410387.6  273687.8  288590.2  137297.5      NA
#> M183T224_POS       NA      NA        NA        NA        NA 5059068.1 5147422
#> M349T47_POS        NA      NA 8730104.8 4105598.5 5141073.2 8424315.6 7896633
#> M182T828_POS  3761893 2572593        NA 3662819.1 5700534.8 4600172.4 5557015
#>                   PS4P4
#> M136T55_2_POS 1005418.8
#> M79T35_POS    3361452.3
#> M307T548_POS   271318.3
#> M183T224_POS         NA
#> M349T47_POS   6441449.0
#> M182T828_POS  4433034.2
slot(object = object, name = "sample_info_note") 
#>              name         meaning
#> 1       sample_id       sample_id
#> 2 injection.order injection.order
#> 3           class           class
#> 4           group           group
slot(object = object, name = "variable_info_note") 
#>          name     meaning
#> 1 variable_id variable_id
#> 2          mz          mz
#> 3          rt          rt
slot(object = object, name = "ms2_data") 
#> list()
slot(object = object, name = "process_info") 
#> $create_mass_dataset
#> -------------------- 
#> pacakge_name: massdataset 
#> function_name: create_mass_dataset() 
#> time: 2026-03-02 09:27:54.550095 
#> parameters:
#> no : no
slot(object = object, name = "annotation_table") 
#> data frame with 0 columns and 0 rows

Use @

mass_data class is a S4 object. So we can also use @.

object@expression_data %>% head()
#>               Blank_3 Blank_4      QC_1      QC_2     PS4P1     PS4P2   PS4P3
#> M136T55_2_POS      NA      NA 1857924.8 1037763.8 1494436.1 3496912.1 1959179
#> M79T35_POS         NA      NA 2821550.2 1304875.3 2471336.1 3333582.7 2734244
#> M307T548_POS       NA      NA  410387.6  273687.8  288590.2  137297.5      NA
#> M183T224_POS       NA      NA        NA        NA        NA 5059068.1 5147422
#> M349T47_POS        NA      NA 8730104.8 4105598.5 5141073.2 8424315.6 7896633
#> M182T828_POS  3761893 2572593        NA 3662819.1 5700534.8 4600172.4 5557015
#>                   PS4P4
#> M136T55_2_POS 1005418.8
#> M79T35_POS    3361452.3
#> M307T548_POS   271318.3
#> M183T224_POS         NA
#> M349T47_POS   6441449.0
#> M182T828_POS  4433034.2
object@sample_info
#>   sample_id injection.order   class   group
#> 1   Blank_3               1   Blank   Blank
#> 2   Blank_4               2   Blank   Blank
#> 3      QC_1               3      QC      QC
#> 4      QC_2               4      QC      QC
#> 5     PS4P1               5 Subject Subject
#> 6     PS4P2               6 Subject Subject
#> 7     PS4P3               7 Subject Subject
#> 8     PS4P4               8 Subject Subject
object@variable_info %>% head()
#>     variable_id        mz        rt
#> 1 M136T55_2_POS 136.06140  54.97902
#> 2    M79T35_POS  79.05394  35.36550
#> 3  M307T548_POS 307.14035 547.56641
#> 4  M183T224_POS 183.06209 224.32777
#> 5   M349T47_POS 349.01584  47.00262
#> 6  M182T828_POS 181.99775 828.35712
object@sample_info_note
#>              name         meaning
#> 1       sample_id       sample_id
#> 2 injection.order injection.order
#> 3           class           class
#> 4           group           group
object@variable_info_note
#>          name     meaning
#> 1 variable_id variable_id
#> 2          mz          mz
#> 3          rt          rt
object@process_info
#> $create_mass_dataset
#> -------------------- 
#> pacakge_name: massdataset 
#> function_name: create_mass_dataset() 
#> time: 2026-03-02 09:27:54.550095 
#> parameters:
#> no : no
object@ms2_data
#> list()
object@annotation_table
#> data frame with 0 columns and 0 rows

Session information

sessionInfo()
#> R version 4.5.2 (2025-10-31)
#> Platform: aarch64-apple-darwin20
#> Running under: macOS Tahoe 26.3
#> 
#> Matrix products: default
#> BLAS:   /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib 
#> LAPACK: /Library/Frameworks/R.framework/Versions/4.5-arm64/Resources/lib/libRlapack.dylib;  LAPACK version 3.12.1
#> 
#> locale:
#> [1] C.UTF-8/C.UTF-8/C.UTF-8/C/C.UTF-8/C.UTF-8
#> 
#> time zone: Asia/Singapore
#> tzcode source: internal
#> 
#> attached base packages:
#> [1] stats     graphics  grDevices utils     datasets  methods   base     
#> 
#> other attached packages:
#>  [1] lubridate_1.9.4    forcats_1.0.0      stringr_1.5.1      purrr_1.1.0       
#>  [5] readr_2.1.5        tidyr_1.3.1        tibble_3.3.0       tidyverse_2.0.0   
#>  [9] magrittr_2.0.3     dplyr_1.1.4        ggplot2_4.0.2      massdataset_0.99.1
#> 
#> loaded via a namespace (and not attached):
#>  [1] tidyselect_1.2.1            farver_2.1.2               
#>  [3] S7_0.2.0                    fastmap_1.2.0              
#>  [5] digest_0.6.37               timechange_0.3.0           
#>  [7] lifecycle_1.0.4             cluster_2.1.8.1            
#>  [9] compiler_4.5.2              rlang_1.1.6                
#> [11] sass_0.4.10                 tools_4.5.2                
#> [13] yaml_2.3.10                 knitr_1.50                 
#> [15] S4Arrays_1.8.1              htmlwidgets_1.6.4          
#> [17] DelayedArray_0.34.1         RColorBrewer_1.1-3         
#> [19] abind_1.4-8                 withr_3.0.2                
#> [21] BiocGenerics_0.54.0         desc_1.4.3                 
#> [23] grid_4.5.2                  stats4_4.5.2               
#> [25] colorspace_2.1-1            scales_1.4.0               
#> [27] iterators_1.0.14            dichromat_2.0-0.1          
#> [29] SummarizedExperiment_1.38.1 cli_3.6.5                  
#> [31] rmarkdown_2.29              crayon_1.5.3               
#> [33] ragg_1.4.0                  generics_0.1.4             
#> [35] rstudioapi_0.17.1           httr_1.4.7                 
#> [37] tzdb_0.5.0                  rjson_0.2.23               
#> [39] cachem_1.1.0                parallel_4.5.2             
#> [41] XVector_0.48.0              matrixStats_1.5.0          
#> [43] vctrs_0.6.5                 Matrix_1.7-4               
#> [45] jsonlite_2.0.0              IRanges_2.42.0             
#> [47] hms_1.1.3                   GetoptLong_1.0.5           
#> [49] S4Vectors_0.48.0            clue_0.3-66                
#> [51] systemfonts_1.2.3           foreach_1.5.2              
#> [53] jquerylib_0.1.4             glue_1.8.0                 
#> [55] pkgdown_2.1.3               codetools_0.2-20           
#> [57] stringi_1.8.7               shape_1.4.6.1              
#> [59] gtable_0.3.6                GenomeInfoDb_1.44.2        
#> [61] GenomicRanges_1.60.0        UCSC.utils_1.4.0           
#> [63] ComplexHeatmap_2.24.1       pillar_1.11.0              
#> [65] htmltools_0.5.8.1           GenomeInfoDbData_1.2.14    
#> [67] circlize_0.4.16             R6_2.6.1                   
#> [69] textshaping_1.0.1           doParallel_1.0.17          
#> [71] evaluate_1.0.4              Biobase_2.68.0             
#> [73] lattice_0.22-7              png_0.1-8                  
#> [75] openxlsx_4.2.8              bslib_0.9.0                
#> [77] Rcpp_1.1.0                  zip_2.3.3                  
#> [79] SparseArray_1.8.1           xfun_0.53                  
#> [81] fs_1.6.6                    MatrixGenerics_1.20.0      
#> [83] pkgconfig_2.0.3             GlobalOptions_0.1.2